Financial Institutions (NASDAQ: FISI) launches $80M subordinated note exchange

Financial Institutions (NASDAQ: FISI) launches $80M subordinated note exchange

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FAQ

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FAQ

Q: What is Financial Institutions, Inc. (FISI) offering in this S-4 exchange?

Q: Does Financial Institutions, Inc. (FISI) receive cash from this note exchange?

Q: How do the New Notes differ from the Old Notes for FISI investors?

Q: What are key risk factors of the FISI subordinated notes described in the prospectus?

Q: How and when does the interest rate change on FISI’s 2035 subordinated notes?

Q: Will FISI’s New Notes or Old Notes trade on an exchange or have a public market?

What is Financial Institutions, Inc. (FISI) offering in this S-4 exchange?

Does Financial Institutions, Inc. (FISI) receive cash from this note exchange?

How do the New Notes differ from the Old Notes for FISI investors?

What are key risk factors of the FISI subordinated notes described in the prospectus?

How and when does the interest rate change on FISI’s 2035 subordinated notes?

Will FISI’s New Notes or Old Notes trade on an exchange or have a public market?

What are the main business characteristics of Financial Institutions, Inc. supporting these notes?

Positive

Negative

What is Financial Institutions, Inc. (FISI) offering in this S-4 exchange?

Does Financial Institutions, Inc. (FISI) receive cash from this note exchange?

How do the New Notes differ from the Old Notes for FISI investors?

What are key risk factors of the FISI subordinated notes described in the prospectus?

How and when does the interest rate change on FISI’s 2035 subordinated notes?

Will FISI’s New Notes or Old Notes trade on an exchange or have a public market?

What are the main business characteristics of Financial Institutions, Inc. supporting these notes?

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Financial Institutions, Inc. is offering to exchange up to $80,000,000 of registered 6.50% fixed-to-floating rate subordinated notes due 2035 for any and all outstanding unregistered notes of the same series. The exchange satisfies registration rights from the original December 11, 2025 private placement.

The company will not receive any cash proceeds from the exchange offer. New registered notes are issued solely in exchange for Old Notes, which are then cancelled, so total outstanding indebtedness does not increase and the transaction is effectively a non-cash, administrative refinancing of existing obligations.

The New Notes are identical in material economic terms to the Old Notes but are registered with the SEC, generally free of transfer restrictions, and bear a different CUSIP. Holders of New Notes lose registration rights and related additional-interest protections tied to registration defaults under the prior registration rights agreement.

The notes are unsecured, subordinated obligations that rank below senior indebtedness and are structurally subordinated to subsidiary liabilities, including bank deposits. Risks include floating-rate exposure to Three-Month Term SOFR, potential early prepayment, regulatory capital limits on payments, illiquid trading markets and sensitivity to future credit rating changes.

The notes pay a fixed 6.50% rate initially , then switch on December 15, 2030 to a floating rate equal to Three-Month Term SOFR plus 312 basis points. The floating rate resets quarterly based on the then-current benchmark, so interest payments and market value may fluctuate over the remaining term to 2035.

There is currently no public market for either series , and the company does not expect one to develop or intend to list the notes on any national securities exchange or quotation system. As a result, liquidity may be limited and holders might need to hold to maturity or sell via private transactions.

Filing Impact

(Neutral)

Filing Sentiment

(Neutral)

Form Type

S-4

Financial Institutions, Inc. filed an S-4 for an exchange offer covering up to $80,000,000 aggregate principal amount of 6.50% fixed-to-floating rate subordinated notes due 2035. The company will exchange newly registered notes for any and all outstanding unregistered notes issued in a December 11, 2025 private placement.

The New Notes have the same economic terms and share the same indenture as the Old Notes, but are SEC-registered, generally freely transferable, and carry no ongoing registration rights or additional-interest features. The company will receive no cash proceeds, and total indebtedness will not increase, as Old Notes tendered are cancelled.

The prospectus details risks tied to the exchange mechanics, subordination to senior and subsidiary obligations, regulatory capital constraints, floating-rate reliance on Three-Month Term SOFR plus 312 basis points after December 15, 2030, optional prepayment features, potential market illiquidity and sensitivity to future credit ratings.

01/30/2026 - 04:05 PM

As filed with the Securities and Exchange Commission on January 30, 2026

Registration No. 333-

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-4

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

FINANCIAL INSTITUTIONS, INC.

(Exact name of registrant as specified in its charter)

New York

6022

16-0816610

(State or other jurisdiction of

incorporation or organization)

(Primary Standard Industrial

Classification Code Number)

(I.R.S. Employer

Identification Number)

220 Liberty Street

Warsaw, New York 14569

(585) 786-1100

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Samuel J. Burruano, Jr.

Executive Vice President and Chief Legal Officer

Financial Institutions, Inc.

220 Liberty Street

Warsaw, New York 14569

(585) 786-1100

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Benjamin M. Azoff, Esq.

Elizabeth A. Cook, Esq.

Luse Gorman, PC

5335 Wisconsin Avenue, NW, Suite 780

Washington, DC 20015

(202) 274-2000

Approximate date of commencement of proposed sale of the securities to the public: As soon as practicable after this registration statement becomes effective.

If the securities being registered on this Form are being offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box. ☐

If this form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transaction period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

If applicable, place an X in the box to designate the appropriate rule provision relied upon in conducting this transaction:


Exchange Act Rule 13e-4(i) (Cross-Border Issuer Tender Offer)		☐
Exchange Act Rule 14d-1(d) (Cross-Border Third-Party Tender Offer)		☐

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until the registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

THE INFORMATION IN THIS PROSPECTUS IS NOT COMPLETE AND MAY BE CHANGED. A REGISTRATION STATEMENT RELATING TO THESE SECURITIES HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION. WE MAY NOT COMPLETE THE EXCHANGE OFFER AND ISSUE THESE SECURITIES UNTIL SUCH REGISTRATION STATEMENT IS EFFECTIVE. THIS PROSPECTUS IS NOT AN OFFER TO SELL THESE SECURITIES AND IT IS NOT SOLICITING AN OFFER TO BUY THESE SECURITIES IN ANY JURISDICTION WHERE THE OFFER OR SALE IS NOT PERMITTED.

SUBJECT TO COMPLETION, DATED JANUARY 30, 2026

PROSPECTUS

LOGO

Offer to Exchange

Up to $80,000,000 in aggregate principal amount of

6.50% Fixed-to-Floating Rate Subordinated Notes due 2035

that have been registered under the Securities Act of 1933, as amended,

for any and all outstanding unregistered

6.50% Fixed-to-Floating Rate Subordinated Notes due 2035

The exchange offer will expire at 5:00 p.m., Eastern Time, on [expiration date], unless extended.

We are offering to exchange 6.50% Fixed-to-Floating Rate Subordinated Notes due 2035 that have been registered under the Securities Act of 1933, as amended, which we refer to in this prospectus as the “New Notes,” for any and all of our outstanding unregistered 6.50% Fixed-to-Floating Rate Subordinated Notes due 2035 that we issued in a private placement on December 11, 2025, which we refer to in this prospectus as the “Old Notes.” We are offering to exchange the New Notes for the Old Notes to satisfy our obligations under a registration rights agreement that we entered into with the purchasers of the Old Notes in connection with our issuance of the Old Notes to those purchasers.

We will not receive any cash proceeds from the exchange offer. The issuance of the New Notes in exchange for the Old Notes will not result in any increase in our outstanding indebtedness. Old Notes that are not exchanged for New Notes in the exchange offer will remain outstanding. The exchange offer is not subject to any minimum tender condition, but is subject to certain customary conditions.

Subject to the terms of the exchange offer, following the expiration or termination of the exchange offer, we will exchange Old Notes that have been validly tendered and not validly withdrawn before such expiration or termination for an equal principal amount of New Notes. The terms of the New Notes are identical in all material respects to the terms of the Old Notes, except that: (1) the New Notes have been registered with the Securities and Exchange Commission under the Securities Act of 1933, as amended, and, as a result, will not bear any legend restricting their transfer; (2) the New Notes bear a different CUSIP number from the Old Notes; (3) the New Notes are generally not subject to transfer restrictions; (4) holders of the New Notes are not entitled to registration rights under the registration rights agreement that we entered into with the purchasers of the Old Notes; and (5) because the holders of the New Notes are not entitled to registration rights, holders of the New Notes will not have the right to additional interest under the circumstances described in that registration rights agreements relating to our fulfillment of our registration obligations. Following fulfillment of our registration obligations, the accrual of any additional interest on the Old Notes will cease as well. The New Notes evidence the same debt as the Old Notes and are governed by the same indenture under which the Old Notes were issued.

There is no existing public market for the Old Notes or the New Notes, and we do not expect any public market to develop in the future for either the Old Notes or the New Notes. The Old Notes are not listed on any national securities exchange or quotation system, and we do not intend to list the New Notes on any national securities exchange or quotation system.

Except as otherwise provided in this prospectus, you may validly withdraw your tender of Old Notes at any time before 5:00 p.m., Eastern Time, on [expiration date], the expiration date of the exchange offer.

Any broker-dealer that holds Old Notes acquired for its own account as a result of market-making activities or other trading activities and that receives New Notes for its own account pursuant to the exchange offer may be a statutory underwriter and must acknowledge that it will deliver a prospectus meeting the requirements of the Securities Act of 1933, as amended, in connection with any resale of such New Notes. A broker-dealer that acquired Old Notes because of market-making or other trading activities may use this prospectus, as supplemented or amended from time to time, in connection with resales of the New Notes for 180 days after the completion of the exchange offer. See “Plan of Distribution.”

Investing in our securities involves certain risks. See “Risk Factors” beginning on page 10, as well as the risk factors contained in our Annual Report on Form 10-K for the year ended December 31, 2024, and in the other reports filed by us with the Securities and Exchange Commission and incorporated by reference into this prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The securities are not savings accounts, deposits or obligations of any bank and are not insured by the Federal Deposit Insurance Corporation or any other governmental agency.

The date of this prospectus is , 2026

TABLE OF CONTENTS


About this Prospectus			ii
Where You Can Find More Information			iii
Incorporation of Certain Documents by Reference			iii
Cautionary Note Regarding Forward-Looking Statements			v
Summary			1
Risk Factors			10
Use of Proceeds			20
The Exchange Offer			20
Description of the Notes			30
Material United States Federal Income Tax Considerations			47
Plan of Distribution			48
Legal Matters			49
Experts			49

ABOUT THIS PROSPECTUS

This prospectus is part of a Registration Statement on Form S-4, which we refer to as the “registration statement,” that we have filed with the Securities and Exchange Commission, which we refer to as the “SEC,” under the Securities Act of 1933, as amended, which we refer to as the “Securities Act.” This prospectus does not contain all the information set forth in the registration statement, certain parts of which are omitted in accordance with the rules and regulations of the SEC. For further information about us, the exchange offer and the securities offered by this prospectus, reference is made to the registration statement, including the exhibits to the registration statement and the documents incorporated by reference therein.

We are providing this prospectus to holders of Old Notes in connection with our offer to exchange Old Notes for New Notes. We are not making the exchange offer to, nor will we accept tenders for exchange from, holders of Old Notes in any jurisdiction in which the exchange offer or the acceptance of the exchange offer would not be in compliance with the securities or blue sky laws of such jurisdiction.

You should read this prospectus together with the additional information incorporated by reference in this prospectus and in the accompanying letter of transmittal filed by us with the SEC. We have not authorized any other person to provide you with any other information regarding the exchange offer. If anyone provides you with information that is different or inconsistent, you should not rely on it. You should not assume that any information contained in or incorporated by reference into the registration statement, of which this prospectus is a part, is accurate as of any date other than the date of the applicable document that contains such information. Our business, financial condition, results of operations and prospects may have changed since such date.

The registration statement of which this prospectus is a part, including the exhibits to the registration statement, contains additional information about us and the securities offered under this prospectus. The registration statement can be obtained at no cost from the SEC’s website (http://www.sec.gov). Copies of certain information filed by us with the SEC are also available on the Financial Institutions, Inc. website (www.fisi-investors.com) at no cost. Information contained on, or accessible from, the Financial Institutions, Inc. website is expressly not incorporated by reference into this prospectus, and you should not consider it part of this prospectus or any other filings we make with the SEC.

You should not consider any information in this prospectus to be investment, legal or tax advice. You should consult your own counsel, accountant and other advisors for legal, tax, business, financial and related advice regarding the exchange offer and ownership of these securities.

Any broker-dealer that holds Old Notes acquired for its own account as a result of market-making activities or other trading activities and receives New Notes for its own account pursuant to the exchange offer may be a statutory underwriter and must acknowledge that it will deliver a prospectus meeting the requirements of the Securities Act in connection with any resale of such New Notes. This prospectus, as it may be amended or supplemented from time to time, may be used by any such broker-dealer in connection with any resale of New Notes received in exchange for such Old Notes. We will make additional copies of this prospectus, and any amendments or supplements hereto, available to any such broker-dealer that requests it in accordance with the instructions in the letter of transmittal. See “Plan of Distribution.”

Unless otherwise indicated or the context otherwise requires, as used in this prospectus, the terms “we,” “us,” “our” or the “Company” refer to Financial Institutions, Inc. and its consolidated subsidiaries, and the term the “Bank” refers to Five Star Bank, the wholly-owned subsidiary of the Company.

WHERE YOU CAN FIND MORE INFORMATION

We are subject to the reporting requirements of the Securities Exchange Act of 1934, as amended, which we refer to as the “Exchange Act,” and therefore we file annual, quarterly and current reports, proxy statements and other documents with the SEC. Our SEC filings are available on the SEC’s website at www.sec.gov or on our website at www.fisi-investors.com. The reference to our website is not intended to be an active link and the information on, or that can be accessed through, our website is not, and you must not consider the information to be, a part of this prospectus or any other filings that we make with the SEC. See “Incorporation of Certain Documents by Reference” for more information on documents incorporated by reference into this prospectus.

We have filed with the SEC a registration statement on Form S-4 relating to the New Notes and the exchange offer. This prospectus is a part of the registration statement and, as permitted by SEC rules, does not contain all the information in the registration statement. The registration statement, including the exhibits thereto, contains additional relevant information about us, the New Notes and the exchange offer.

INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

The SEC allows us to “incorporate by reference” in this prospectus the information in other documents that we file with the SEC, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus and should be read with the same care. When we update the information contained in documents that have been incorporated by reference, by making future filings with the SEC, the information incorporated by reference in this prospectus is considered to be automatically updated and superseded. In other words, in all cases, if you are considering whether to rely on information contained in this prospectus or information incorporated by reference into this prospectus, you should rely on the information contained in the document that was filed later. We incorporate by reference (other than any information furnished to, rather than filed with, the SEC, unless expressly stated otherwise therein) the documents listed below, which are considered to be a part of this prospectus:

•

our Annual Report on Form 10-K for the year ended December 31, 2024 filed with the SEC on March 12, 2025 (including the portions of our Definitive Proxy Statement on Schedule 14A, filed with the SEC on April 14, 2025, incorporated by reference therein) (File No. 000-26481);

•

our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2025, June 30, 2025 and September 30, 2025, filed with the SEC on May 5, 2025, August 4, 2025 and November 3, 2025, respectively (File No. 000-26481); and

•

our Current Reports on Form 8-K (other than those portions furnished under Items 2.02 or 7.01 of Form 8-K) filed on January 27, 2025, March 6, 2025, March 6, 2025, March 10, 2025, May 29, 2025 and December 11, 2025 (File No. 000-26481).

All other documents that we subsequently file with the SEC pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act, after the initial date of the registration statement of which this prospectus is a part until the later of (1) the termination or completion of the exchange offer or (2) the termination of the period of time described under “Plan of Distribution” during which we have agreed to make available this prospectus to broker-dealers in connection with certain resales of the New Notes, are deemed to be incorporated by reference herein (other than any information furnished to, rather than filed with, the SEC, unless expressly stated otherwise therein).

iii

Holders of Old Notes can also obtain these documents from us, without charge (other than exhibits, unless the exhibits are specifically incorporated by reference), upon written or oral request at the following address and telephone number:

Financial Institutions, Inc.

Attn: Samuel J. Burruano, Jr.

Executive Vice President and Chief Legal Officer

220 Liberty Street, Warsaw, New York 14569

Telephone: (585) 786-1100

To ensure timely delivery of any requested information, holders of the Old Notes must make any request no later than , 2026, which is five business days before the expiration date of the exchange offer, or, if we decide to extend the expiration date of the exchange offer, no later than five business days before such extended expiration date.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus may contain forward-looking statements, which may be identified by the use of such words as “annualized,” “anticipate,” “believe,” “continue,” “estimate,” “expect,” “focus,” “forecast,” “intend,” “may,” “plan,” “preliminary,” “should,” “target” or “will,” and words of similar meaning. These forward-looking statements include, but are not limited to, statements with respect to the beliefs, plans, objectives, goals, guidelines, expectations, anticipations, and future financial condition, results of operations, and performance of the Company and its subsidiaries.

These forward-looking statements are based on current beliefs and expectations of our management and are inherently subject to significant business, economic and competitive uncertainties and contingencies, many of which are beyond our control. In addition, these forward-looking statements are based upon assumptions with respect to future business strategies and decisions that are subject to change. Forward-looking statements involve significant risks and uncertainties and actual results may differ materially from those expressed or implied in this prospectus. Factors that might cause material differences include, but are not limited to:

•

If we experience greater credit losses than anticipated, earnings may be adversely impacted;

•

We are subject to risks and losses resulting from fraudulent activities that could adversely impact our financial performance and results of operations;

•

Geographic concentration in our loan portfolio may unfavorably impact our operations;

•

Our commercial business and commercial mortgage loans increase our exposure to credit risks;

•

If our non-performing assets increase, our earnings will be adversely affected;

•

If our regulators impose limitations on our commercial real estate lending activities, earnings could be adversely affected;

•

Our indirect and consumer lending involves risk elements in addition to normal credit risk;

•

Lack of seasoning in portions of our loan portfolio could increase risk of credit defaults in the future;

•

We accept deposits that do not have a fixed term, and which may be withdrawn by the customer at any time for any reason;

•

Municipal deposits are price sensitive and could result in an increase in interest expense or funding fluctuations;

•

We are subject to environmental liability risk associated with our lending activities;

•

We operate in a highly competitive industry and market area;

•

Legal and regulatory proceedings and related matters could adversely affect us and the banking industry in general;

•

Any future Federal Deposit Insurance Corporation (“FDIC”) insurance premium increases may adversely affect our earnings;

•

We are highly regulated, and any adverse regulatory action may result in additional costs, loss of business opportunities, and reputational damage;

•

Non-compliance with the USA PATRIOT Act, the Bank Secrecy Act, and Office of Foreign Asset Control sanction requirements, amount other laws and regulations, could subject us to fines, sanctions, or other negative actions;

•

We are subject to the Community Reinvestment Act (the “CRA”) and fair lending laws, and failure to comply with these laws could lead to material penalties;

•

The policies of the Federal Reserve Board have a significant impact on our earnings;

•

We have implemented a program to provide financial products and services to customers that do business in the cannabis industry and the strict enforcement of federal laws and regulations regarding cannabis could result in our inability to continue to provide financial products and services to these customers and we could have legal action taken against us by the federal government and exposure to additional liabilities and regulatory compliance costs;

•

Our investment advisory and wealth management operations are subject to risk related to the regulation of the financial services industry and market volatility;

•

We make certain assumptions and estimates in preparing our financial statements that may prove to be incorrect, which could significantly impact our results of operations, cash flows and financial condition, and we are subject to new or changing accounting rules and interpretations, and the failure by us to correctly interpret or apply these evolving rules and interpretations could have a material adverse effect;

•

The value of our goodwill and other intangible assets may decline in the future;

•

We may be unable to successfully implement our growth strategies, including the integration and successful management of newly-acquired businesses and expansion of our commercial lending footprint;

•

Acquisitions may disrupt our business and dilute shareholder value;

•

Our tax strategies and the value of our deferred tax assets and liabilities could adversely affect our operating results and regulatory capital ratios;

•

Liquidity is essential to our businesses;

•

We rely on dividends from our subsidiaries for most of our revenue;

•

If our risk management framework does not effectively identify or mitigate our risks, we could suffer losses;

•

We are subject to interest rate risk, and fluctuations in market interest rates may affect our interest margins and income, demand for our products, defaults on loans, loan prepayments and the fair value of our financial instruments;

•

The soundness of other financial institutions could adversely affect us;

•

We may need to raise additional capital in the future and such capital may not be available on acceptable terms or at all;

•

Emerging technology, including cloud computing and artificial intelligence, introduces new risks while possibly being essential to support business strategy;

•

We rely on third parties to provide critical business services and protect the confidentiality, integrity, and availability of confidential data;

•

We, or our service providers, may experience a cyber-attack, system failure, natural disaster, or other uncontrollable event that may disrupt business operations;

•

We are subject to evolving laws and regulations relating to cybersecurity protection and data privacy, and failure to comply could expose us to regulatory liability, reputational risk and financial risk;

•

We may issue debt and equity securities or securities convertible into equity securities, any of which may be senior to our common stock or subordinated debt as to distributions and in liquidation;

•

Our certificate of incorporation, our bylaws, and certain banking laws may have an anti-takeover effect;

•

We may not be able to attract and retain skilled people;

•

Loss of key employees may disrupt relationships with certain customers;

•

We use financial models for business planning purposes that may not adequately predict future results;

•

We depend on the accuracy and completeness of information about or from customers and counterparties;

•

Our business may be adversely affected by conditions in the financial markets and economic conditions generally, including macroeconomic pressures such as inflation, tariffs, supply chain issues, and geopolitical risks associated with international conflict;

•

Severe weather, natural disasters, public health emergencies and pandemics, acts of war or terrorism, and other external events could significantly impact our business;

•

Negative public opinion could damage our reputation and impact business operations and revenues; and

•

Environmental, social and governance matters, and any related reporting obligations may impact our business.

A discussion of these and other factors that could affect our results is included in our filings with the Securities and Exchange Commission, including our Annual Report on Form 10-K for the year ended December 31, 2024 and subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K. Because of these and other uncertainties, our actual future results may be materially different from the results indicated by these forward-looking statements. Accordingly, you should not place undue reliance on such statements. Except as required by law, we disclaim any intention or obligation to update or revise any forward-looking, whether as a result of new information, future events or otherwise.

vii

SUMMARY

This summary highlights selected information appearing elsewhere in, or incorporated by reference into, this prospectus and is therefore qualified in its entirety by the more detailed information appearing elsewhere in, or incorporated by reference into, this prospectus. This summary may not contain all of the information that may be important to you or that you should consider in deciding to exchange your Old Notes for New Notes. We urge you to read carefully this entire prospectus and the other documents to which it refers to understand fully the terms of the New Notes and the exchange offer. You should pay special attention to the sections entitled “Risk Factors” and “Cautionary Note Regarding Forward-Looking Statements.”

Financial Institutions, Inc.

Financial Institutions, Inc. is a New York corporation, organized in 1931, and registered with the Federal Reserve as a financial holding company. The Company owns all of the capital stock of Five Star Bank. The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, which include the Bank and Courier Capital, LLC.

The Bank is a New York state-chartered bank. As a state-chartered member bank of the Federal Reserve System, the Bank is regulated primarily by the New York State Department of Financial Services and the Federal Reserve Bank of New York. The Bank has a total of 48 full-service banking offices in the New York State counties of Allegany, Cattaraugus, Cayuga, Chemung, Erie, Genesee, Livingston, Monroe, Ontario, Orleans, Seneca, Steuben, Wyoming and Yates, and commercial loan production offices in Baltimore, Maryland, and Syracuse, New York, serving the Mid-Atlantic and Central New York regions, respectively. The Bank offers deposit products, which include checking and NOW accounts, savings accounts, and certificates of deposit, as its principal source of funding. The Bank’s deposits are insured up to the maximum permitted by the Deposit Insurance Fund of the FDIC. The Bank offers a variety of loan products to its customers, including commercial and consumer loans.

Courier Capital is an SEC-registered investment advisory and wealth management firm founded in 1967 and headquartered in Western New York, with offices in Buffalo, Rochester and Jamestown, New York, and Pittsburgh, Pennsylvania. With $3.56 billion in assets under management as of September 30, 2025, Courier Capital offers customized investment advice, wealth management, investment consulting and retirement plan services to individuals, businesses and institutions. For the nine months ended September 30, 2025, Courier Capital had total revenue of $8.7 million.

As of September 30, 2025, we had consolidated total assets of $6.29 billion, total deposits of $5.36 billion and total shareholders’ equity of $621.7 million. Our principal executive offices are located at 220 Liberty Street, Warsaw, New York 14569, and our telephone number is (585) 786-1100. The Company’s common stock is traded on the Nasdaq Global Select Market under the symbol “FISI.”

Additional information about the Company and its subsidiaries may be found in the documents incorporated by reference into this prospectus. See “Where You Can Find More Information.”

Summary of the Exchange Offer

The following provides a summary of certain terms of the exchange offer. See “The Exchange Offer” appearing elsewhere in this prospectus for a more complete description of the exchange offer and “Description of the Notes” for a more complete description of the terms of the Old Notes and New Notes.

Old Notes

$80,000,000 in aggregate principal amount of 6.50% Fixed-to-Floating Rate Subordinated Notes due 2035.

New Notes

Up to $80,000,000 in aggregate principal amount of 6.50% Fixed-to-Floating Rate Subordinated Notes due 2035 that have terms that are identical in all material respects to the terms of the Old Notes, except that: (1) the New Notes have been registered with the SEC under the Securities Act and, as a result, will not bear any legend restricting their transfer; (2) the New Notes bear a different CUSIP number from the Old Notes; (3) the New Notes are generally not subject to transfer restrictions; (4) holders of the New Notes are not entitled to registration rights under the registration rights agreement that we entered into with the purchasers of the Old Notes or otherwise; and (5) because the holders of the New Notes are not entitled to registration rights, holders of the New Notes will not have the right to additional interest under the circumstances described in the registration rights agreements relating to our fulfillment of our registration obligations.

Exchange Offer

We are offering to exchange the Old Notes for a like principal amount of New Notes. Subject to the terms of the exchange offer, following the expiration or termination of the exchange offer, we will exchange Old Notes that have been validly tendered and not validly withdrawn before such expiration or termination for an equal principal amount of New Notes.

Expiration Date

The exchange offer will expire at 5:00 p.m., Eastern Time, on [expiration date], unless extended.

Withdrawal Rights for Old Notes Issued in
Book-Entry Form

Except as otherwise provided in this prospectus, you may validly withdraw your book-entry tender of Old Notes at any time before 5:00 p.m., Eastern Time, on the expiration date. For a withdrawal of tendered Old Notes issued in book-entry form to be effective, the exchange agent must receive, on or before 5:00 p.m., Eastern Time, on the expiration date, a computer-generated notice of withdrawal, transmitted by the Depository Trust Company, which we refer to as the “DTC,” on your behalf in accordance with the appropriate procedures of DTC’s Automated Tender Offer Program, which we refer to as “ATOP.” See “The Exchange Offer—Withdrawal of Tenders.”

Withdrawal Rights for Old Notes Issued in
Certificated Form

Except as otherwise provided in this prospectus, you may validly withdraw your certificated tender of Old Notes at any time prior to 5:00 p.m., Eastern Time, on the expiration date. For a withdrawal of tendered Old Notes in certificated form to be effective, the exchange agent must receive a written notice of withdrawal prior to 5:00 p.m., Eastern Time, on the expiration date. See “The Exchange Offer—Withdrawal of Tenders.”

Conditions to Exchange Offer

The exchange offer is subject to customary conditions, which we may waive. See “The Exchange Offer—Conditions.”

Procedures for Tendering Old Notes Issued in Book Entry Form

Some of the Old Notes were issued in book-entry form, and are currently represented by a global certificate held for the account of DTC, as depositary. DTC or its nominee is treated as the registered holder of the Old Notes and will be the only entity that can tender your Old Notes for New Notes.

To participate in the exchange offer, you must follow the procedures established by DTC for tendering Old Notes held in book-entry form. DTC’s ATOP procedures require that, before the expiration date of the exchange offer, (1) DTC receives (a) your instructions to exchange your Old Notes and (b) your agreement to be bound by the terms of the accompanying letter of transmittal, and (2) the exchange agent receives a computer-generated message known as an “agent’s message” that is transmitted through ATOP.

By using the ATOP procedures to tender and exchange Old Notes, you will be bound by the terms of the letter of transmittal that accompanies this prospectus, and you will be deemed to have made the acknowledgments and representations it contains. See “The Exchange Offer—Eligibility; Transferability” and “The Exchange Offer—Representations.”

Procedures for Tendering Old Notes Issued in Certificated Form

Some of the Old Notes were issued in certificated form. For any Old Notes that are in certificated form and that are registered in the initial purchaser’s name, each holder of an Old Note must transmit a properly completed and duly executed letter of transmittal, the certificated note, and any other documents required by the letter of transmittal to the exchange agent, at its address listed under “The Exchange Offer—Exchange Agent.” By signing, or agreeing to be bound by, the letter of transmittal, you will be making a number of acknowledgments and representations to us. See “The Exchange Offer—Eligibility; Transferability” and “The Exchange Offer—Representations.”

Material United States Federal Income Tax Considerations

The exchange of Old Notes for New Notes in the exchange offer generally should not constitute a taxable event for U.S. federal income tax purposes. See “Material United States Federal Income Tax Considerations.” You should consult your own tax advisor as to the tax consequences of exchanging your Old Notes for New Notes.

Registration Rights

Under the terms of the registration rights agreements that we entered into with the purchasers of the Old Notes at the time we issued the Old Notes, we agreed to register the New Notes and undertake the exchange offer. The exchange offer is intended to satisfy the rights of holders of Old Notes under those registration rights agreements. After the exchange offer is completed, we will have no further obligations, except under certain limited circumstances, to provide for any

exchange or undertake any further registration with respect to the Old Notes.

Transferability

Based on existing interpretations of the Securities Act by the staff of the SEC set forth in several no-action letters issued to other parties, we believe that you may offer for resale, resell or otherwise transfer the New Notes without complying with the registration and prospectus delivery requirements of the Securities Act, provided that:

•

you are acquiring the New Notes in the ordinary course of business;

•

you do not have an arrangement or understanding with any person to participate in any distribution (within the meaning of the Securities Act) of the New Notes;

•

you are not an “affiliate” of ours within the meaning of Rule 405 under the Securities Act;

•

you are not a broker-dealer registered under the Exchange Act, and you are not engaged in, nor is any such person engaged in, and do not intend to engage in, any distribution (within the meaning of the Securities Act) of the New Notes; and

•

you are not acting on behalf of any person who could not truthfully make these statements.

Our belief that transfers of New Notes would be permitted without complying with the registration and prospectus delivery requirements of the Securities Act under the conditions described above is based on interpretations by the staff of the SEC given to other, unrelated issuers in similar exchange offers. The staff of the SEC has not considered this exchange offer in the context of a no-action letter, and we cannot assure you that the staff of the SEC would make a similar interpretation with respect to this exchange offer. If our belief is not accurate and you transfer a New Note without delivering a prospectus meeting the requirements of the Securities Act or without an exemption from such requirements, you may incur liability under the Securities Act. We do not and will not assume, or indemnify you against, such liability. See “Risk Factors—Risks Related to the Exchange Offer.”

Consequences of Failing to Exchange Old Notes

Any Old Notes that are not exchanged in the exchange offer will continue to be governed by the applicable indenture relating to the

Old Notes and the terms of the Old Notes. Old Notes that are not exchanged will remain “restricted securities” within the meaning of Rule 144(a)(3) under the Securities Act and will be subject to the restrictions on transfer described in the Old Notes, and you will generally not be able to offer, sell, pledge or otherwise transfer the Old Notes, except to us or to any of our subsidiaries, under a registration statement that has been declared effective under the Securities Act or under an exemption from the requirements of the Securities Act. Upon the completion of the exchange offer, we will have no further obligations, except under limited circumstances, to provide for any exchange or undertake any further registration with respect to the Old Notes, and any accrual of additional interest on the Old Notes will cease. If you do not participate in the exchange offer, the liquidity of your Old Notes could be adversely affected. See “Risk Factors—Risks Related to the Exchange Offer” and “The Exchange Offer—Consequences of Failure to Exchange.”

Use of Proceeds

We will not receive any cash proceeds from the exchange of Old Notes for New Notes because of the exchange offer. Subject to certain exceptions, we will pay all expenses incident to the exchange offer.

Cancellation of Exchanged Old Notes

Old Notes that are surrendered in exchange for New Notes will be retired and cancelled and will not be reissued. Accordingly, the issuance of the New Notes under the exchange offer will not result in any increase in our outstanding indebtedness.

Exchange Agent

Wilmington Trust, National Association is serving as the exchange agent for the exchange offer. See “The Exchange Offer—Exchange Agent” for the address, telephone number and email address of the exchange agent.

Summary of the New Notes

The following provides a summary of certain terms of the New Notes. The New Notes have terms that are identical in all material respects to the terms of the Old Notes, except that: (1) the New Notes have been registered with the SEC under the Securities Act and, as a result, will not bear any legend restricting their transfer; (2) the New Notes bear a different CUSIP number from the Old Notes; (3) the New Notes are generally not subject to transfer restrictions; (4) holders of the New Notes are not entitled to registration rights under the registration rights agreement that we entered into with the purchasers of the Old Notes; and (5) because the holders of the New Notes are not entitled to registration rights, holders of the New Notes will not have the right to additional interest under the circumstances described in the registration rights agreements relating to our fulfillment of our registration obligations. The New Notes will evidence the same debt as the Old Notes and will be governed by the same indenture under which the Old Notes were issued. See “Description of the Notes” for a more complete description of the terms of the New Notes. References in this prospectus to the “notes” include both the Old Notes and the New Notes unless otherwise indicated or the context otherwise requires. Unless otherwise indicated or the context otherwise requires, as used in this summary, “we,” “our,” “us” and the “Company” refer only to Financial Institutions, Inc. and not to any of its subsidiaries.

Issuer

Financial Institutions, Inc.

Securities

6.50% Fixed-to-Floating Rate Subordinated Notes due 2035.

Aggregate Principal Amount

$80,000,000

Stated Maturity

December 15, 2035, unless previously prepaid.

Form and Denomination

The New Notes will be issued only in registered form without coupons and in minimum denominations of $100,000 and any integral multiple of $1,000 in excess thereof. Unless otherwise required for institutional accredited investors, the New Notes will be evidenced by a global note deposited with the trustee for the New Notes, as custodian for DTC, and transfers of beneficial interests will be facilitated only through records maintained by DTC and its participants.

Interest Rate and Interest Rate Payment Dates During Fixed Interest Period

Interest Rate and Interest Rate Payment Dates During Floating Interest Period

From, and including, December 15, 2030 to, but excluding, December 15, 2035, unless prepaid before December 15, 2035 (such period, the “floating rate period”), at a rate equal to Three-Month Term SOFR, reset quarterly, plus 312 basis points, or such other rate as determined pursuant to the indenture, payable quarterly in arrears on March 15, June 15, September 15 and December 15 of each year through December 15, 2035 or earlier prepayment date. If Three-Month Term SOFR (or other applicable floating interest rate) is less

than zero, then Three-Month Term SOFR (or other such applicable floating interest rate) shall be deemed to be zero.

If the calculation agent determines on or before the relevant Reference Time that a Benchmark Transition Event and its related Benchmark Replacement Date each as defined under “Description of the Notes—Effect of Benchmark Transition Event”) have occurred with respect to Three-Month Term SOFR, then the provisions under “Description of the Notes—Effect of Benchmark Transition Event,” which are referred to herein as the “benchmark transition provisions,” will thereafter apply to all determinations of the interest rate on the notes for each interest period during the floating rate period. In accordance with the benchmark transition provisions, after a Benchmark Transition Event and its related Benchmark Replacement Date have occurred, the interest rate on the notes for each interest period during the floating rate period will be an annual rate equal to the Benchmark Replacement (as defined under “Description of the Notes—Effect of Benchmark Transition Event”) plus 312 basis points.

Day Count Convention

During the Fixed Interest Period: 30-day month/360-day year.

During the Floating Interest Period: 360-day year and the number of actual days elapsed.

Record Dates

We will make each interest payment to the holders of record of the New Notes at the close of business on the fifteenth calendar day before the applicable interest payment date, without regard to whether such day is a business day.

Subordination; Ranking

The New Notes will be our general unsecured, subordinated obligations and:

•

will rank junior in right of payment and upon liquidation to our existing and future “senior indebtedness” (as defined below);

•

will rank equally in right of payment and upon liquidation to our existing and future unsecured indebtedness, the terms of which provide that such indebtedness ranks equally with promissory notes, bonds, debentures and other evidences of indebtedness of types that include the New Notes;

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will rank senior in right of payment and upon liquidation to our existing and future indebtedness, the terms of which provide that such indebtedness ranks junior to promissory notes, bonds, debentures and other evidences of indebtedness of types that include the New Notes; and

•

will be effectively subordinated to the existing and future indebtedness, deposits and other liabilities of the Company and our subsidiaries, including without limitation the Bank’s deposit liabilities and claims of other creditors of the Bank.

As of September 30, 2025, the Company’s subsidiaries had, in the aggregate, outstanding debt and deposits of $5.6 billion. In addition, as of September 30, 2025, the Company had no indebtedness that would rank senior to the New Notes, no indebtedness that would rank pari passu with the New Notes (other than the Old Notes), and no indebtedness that would rank subordinate to the New Notes.

See “Description of the Notes—Subordination.”

Optional Prepayment

We may, at our option, prepay the New Notes (1) in whole or in part on or after December 15, 2030, and (2) in whole or in part at any time upon the occurrence of a Tier 2 Capital Event, Tax Event or an Investment Company Event (each as defined in “Description of the Notes—Prepayment”).

Any prepayment of the New Notes will be at a prepayment price equal to 100% of the principal amount of the notes to be prepaid, plus accrued and unpaid interest to, but excluding, the date of prepayment. Any prepayment of the New Notes will be subject to any required regulatory approvals, including from the Federal Reserve, to the extent such approval is then required.

The New Notes will not be entitled to the benefit of any sinking fund.

No Limitations on Indebtedness

The indenture governing the New Notes and the terms of the New Notes do not contain any covenants or restrictions on the incurrence of indebtedness or other obligations by us or by a subsidiary of ours, including the Bank.

Limited Indenture Covenants

The indenture governing the New Notes contains no financial covenants requiring us to achieve or maintain any minimum financial results relating to our financial position or results of operations or meet or exceed any financial ratios as a general matter or to incur additional indebtedness or obligations or to maintain any reserves.

Moreover, neither the indenture nor the New Notes contain any covenants limiting our right to grant liens on our assets to secure our indebtedness or other obligations that are senior in right of payment to the New Notes, repurchase our stock or other securities, including any of the New Notes, or pay dividends or make other distributions to our shareholders (except, subject to certain limited exceptions, in the case of dividends or other distributions; redemptions, purchases, acquisitions or liquidation payments with respect to our capital stock; and repayments, repurchases or redemptions of any debt securities that rank equal with or junior to the notes, in each case, upon an event of default).

Listing; No Public Market

The New Notes are a new issue of securities with no established trading market and we do not expect any public market to develop in the future for the New Notes. The Old Notes are not listed on any

national securities exchange or quotation system and we do not intend to apply for listing of the New Notes on any national securities exchange or quotation system.

Risk Factors

See “Risk Factors” beginning on page 10 of this prospectus, as well as the sections entitled “Risk Factors” in our annual and quarterly reports filed with the SEC, and other information included in or incorporated by reference into this prospectus for a discussion of factors you should consider carefully before deciding to participate in the exchange offer.

Trustee

Wilmington Trust, National Association, or its successor if replaced in accordance with the provisions of the indenture.

Governing Law

The indenture and the New Notes are governed by and will be construed in accordance with the laws of the State of New York.

RISK FACTORS

In addition to the other information contained in or incorporated by reference into this prospectus, including the matters addressed under “Cautionary Note Regarding Forward-Looking Statements” and the matters discussed under “Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2024, and any updates to those risk factors set forth in our subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, all of which have been filed with the SEC and are incorporated by reference herein, you should carefully consider the following risks in deciding whether to participate in the exchange offer. See “Where You Can Find More Information.” If any of the risks contained in or incorporated by reference into this prospectus develop into actual events, our business, financial condition, liquidity, results of operations and prospects could be materially and adversely affected, the value of the New Notes could decline, our ability to repay the New Notes may be impaired and you may lose all or part of your investment.

Risks Related to our Business

For a discussion of certain risks applicable to our business and operations, see the section entitled “Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2024 and any updates to those risk factors set forth in our subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K.

Risks Related to the Exchange Offer

If you do not tender your Old Notes, you will continue to hold unregistered Old Notes, and your ability to transfer Old Notes will be adversely affected.

We will only issue New Notes in exchange for Old Notes that you timely and validly tender in accordance with the terms of the exchange offer. Therefore, you should allow sufficient time to ensure timely delivery of the Old Notes, and you should carefully follow the instructions on how to tender your Old Notes. Although we intend to request the exchange agent to notify holders of defects or irregularities relating to tenders and withdrawals of Old Notes, neither we, the exchange agent nor any other person will have any duty to give or incur any liability for failure to give such notification. See “The Exchange Offer–Procedures for Tendering Old Notes.”

If you do not exchange your Old Notes for New Notes in the exchange offer, you will continue to be subject to the restrictions on transfer of your Old Notes described in the legend on the certificate for the Old Notes. The transfer of the Old Notes is restricted because we issued the Old Notes in a private placement not subject to registration under the Securities Act or applicable state securities laws. In general, you may only offer or sell the Old Notes if they are registered under the Securities Act and applicable state securities laws, or you offer and sell under an exemption from these requirements. We do not plan to register any sale of the Old Notes under the Securities Act. Additionally, the tender of Old Notes under the exchange offer by other holders will reduce the principal amount of the Old Notes outstanding, which may have an adverse effect upon, and increase the volatility of, the market price of any Old Notes that remain outstanding, due to a reduction in liquidity.

For further information regarding the consequences of failing to exchange your Old Notes in the exchange offer, see “The Exchange Offer–Consequences of Failure to Exchange.”

You may not receive New Notes in the exchange offer if you do not properly follow the exchange offer procedures.

We will issue New Notes in exchange for your Old Notes only if you validly tender and do not validly withdraw your Old Notes before expiration of the exchange offer. Although we intend to request the exchange agent to notify holders of defects or irregularities relating to tenders and withdrawals of Old Notes, neither we, the exchange agent nor any other person will have any duty or incur any liability for failure to give such

notification. If you are the beneficial holder of Old Notes that are held through your broker, dealer, commercial bank, trust company or other nominee, and you wish to tender such Old Notes in the exchange offer, you should promptly contact the person through whom your Old Notes are held and instruct that person to tender your Old Notes on your behalf in accordance with the procedures described in this prospectus and the accompanying letter of transmittal.

Old Notes that are not tendered or that are tendered but not accepted for exchange will, following consummation of the exchange offer, continue to be subject to the existing transfer restrictions under the Securities Act, and upon consummation of the exchange offer, certain registration and other rights under the registration rights agreements that we entered into with the purchasers of the Old Notes will terminate. See “The Exchange Offer—Procedures for Tendering Old Notes” and “The Exchange Offer—Consequences of Failure to Exchange.”

Some holders who exchange their Old Notes may be deemed to be underwriters, and these holders will be required to comply with additional requirements under the Securities Act.

Based on interpretations of the Securities Act by the staff of the SEC contained in certain no-action letters issued to other parties, we believe that you, or any other person receiving New Notes, may offer for resale, resell or otherwise transfer the New Notes without complying with the registration and prospectus delivery requirements of the Securities Act. Our belief that transfers of New Notes would be permitted without registration or prospectus delivery under the conditions described above is based on interpretations by the staff of the SEC given to other, unrelated issuers in similar exchange offers. The staff of the SEC has not considered this exchange offer in the context of a no-action letter, and the staff of the SEC may not make a similar interpretation with respect to this exchange offer. Additionally, in some instances described in this prospectus under “Plan of Distribution,” certain holders of New Notes will remain obligated to comply with the registration and prospectus delivery requirements of the Securities Act to resell the New Notes. If any such holder transfers any New Notes without delivering a prospectus meeting the requirements of the Securities Act or without an applicable exemption from registration under the Securities Act, such holder may incur liability under the Securities Act. We do not and will not assume, or indemnify any such holder or other person against, such liability.

Risks Related to the Notes

The interest rate for the notes during the floating rate period may be determined based on a rate other than Three-Month Term SOFR.

Under the terms of the notes, the interest rate on the notes for each interest period during the applicable floating rate period will be based on Three-Month Term SOFR, a forward-looking term rate for a tenor of three months that will be based on SOFR. SOFR has a limited history, and the future performance of SOFR cannot be predicted based on its limited historical performance. The level of SOFR during the applicable floating rate period for the notes may bear little or no relation to historical actual or indicative data. Prior observed patterns, if any, in the behavior of market variables and their relation to SOFR, such as correlations, may change in the future. While some pre-publication historical data have been released by the Federal Reserve Bank of New York, such analysis involves assumptions, estimates and approximations, and hypothetical or historical performance data are not indicative of, and have no bearing on, the potential performance of SOFR. The future performance of SOFR is therefore impossible to predict, and no future performance of SOFR may be inferred from any of the historical actual or indicative data. Changes in the levels of SOFR will affect the interest rate of the notes during the applicable floating rate period and accordingly will affect the return on the notes and the market price of the notes, but it is impossible to predict whether such levels will rise or fall.

Under the terms of the notes, we are expressly authorized to make determinations, decisions or elections with respect to technical, administrative or operational matters that we decide are appropriate to reflect the use of Three-Month Term SOFR as the interest rate basis for the notes, which are defined in the terms of the indenture

as “Three-Month Term SOFR Conventions.” Our determination and implementation of any Three-Month Term SOFR Conventions could result in adverse consequences to the amount of interest that accrues on the notes during the floating rate period, which could adversely affect the return on, value of and market for the notes.

Any Benchmark Replacement may not be the economic equivalent of Three-Month Term SOFR.

Under the benchmark transition provisions of the notes, if the calculation agent determines that a Benchmark Transition Event and its related Benchmark Replacement Date have occurred with respect to Three-Month Term SOFR, then the interest rate on the notes during the floating rate period will be determined using the next-available Benchmark Replacement (which may include a related Benchmark Replacement Adjustment). However, the Benchmark Replacement may not be the economic equivalent of Three-Month Term SOFR. For example, Compounded SOFR, the first available Benchmark Replacement, is the compounded average of the daily Secured Overnight Financing Rates calculated in arrears, while Three-Month Term SOFR is intended to be a forward-looking rate with a tenor of three months. In addition, very limited market precedent exists for securities that use Compounded SOFR as the rate basis, and the method for calculating Compounded SOFR in those precedents varies. Further, the ISDA Fallback Rate, which is another Benchmark Replacement, may change over time.

The implementation of Benchmark Replacement Conforming Changes could adversely affect the amount of interest that accrues on the notes and the trading prices for the notes.

Under the benchmark transition provisions of the notes, if Three-Month SOFR has been discontinued or if a particular Benchmark Replacement or Benchmark Replacement Adjustment cannot be determined, then the next-available Benchmark Replacement or Benchmark Replacement Adjustment will apply. These replacement rates and adjustments may be selected or formulated by (1) the Relevant Governmental Body, (2) ISDA or (3) in certain circumstances, the calculation agent. In addition, the benchmark transition provisions expressly authorize the calculation agent to make certain changes, which are defined in the terms of the indenture as “Benchmark Replacement Conforming Changes,” with respect to, among other things, the determination of interest periods, and the timing and frequency of determining rates and making payments of interest. The application of a Benchmark Replacement and Benchmark Replacement Adjustment, and any implementation of Benchmark Replacement Conforming Changes, could result in adverse consequences to the amount of interest that accrues on the notes during the floating rate period, which could adversely affect the return on, value of and market for the notes. Further, there is no assurance that the characteristics of any Benchmark Replacement will be similar to the then-current Benchmark that it is replacing, or that any Benchmark Replacement will produce the economic equivalent of the then-current Benchmark that it is replacing.

The notes are unsecured and subordinated to our existing and future senior indebtedness.

The notes are unsecured, subordinated obligations of the Company, and rank junior in right of payment to all of the Company’s current and future senior indebtedness, as described under “Description of the New Notes—Subordination.” As a result, upon any payment or distribution of assets to creditors in the case of liquidation, dissolution, winding up, reorganization, assignment for the benefit of creditors or any bankruptcy, insolvency or similar proceeding, the holders of the senior indebtedness are entitled to have the senior indebtedness paid in full before the holders of the notes receiving any payment of principal of, or interest on, the notes.

As of September 30, 2025, the Company and its subsidiaries had, in the aggregate, outstanding debt and deposits of $5.67 billion. In addition, as of September 30, 2025, the Company had no indebtedness that would rank senior to the New Notes, no indebtedness that would rank pari passu with the New Notes (other than the Old Notes), and no indebtedness that would rank subordinate to the New Notes. The notes do not limit the amount of additional indebtedness or senior indebtedness that we or any of our subsidiaries, including the Bank, may incur. Accordingly, in the future, we and our subsidiaries may incur other indebtedness, which may be substantial in

amount, including senior indebtedness, indebtedness ranking on par with the notes and indebtedness ranking senior to the notes, as applicable. Any additional indebtedness and liabilities that we and our subsidiaries incur may adversely affect our ability to pay our obligations on the notes.

As a consequence of the subordination of the notes to our existing and future senior indebtedness, an investor in the notes may lose all or some of its investment upon our liquidation, dissolution, winding up, reorganization, assignment for the benefit of creditors or any bankruptcy, insolvency or similar proceeding. In such an event, our assets would be available to pay the principal of, and any accrued and unpaid interest on, the notes only after all of our senior indebtedness had been paid in full. In such an event, any of our other general, unsecured obligations that do not constitute senior indebtedness, depending upon their respective preferences, will share ratably in our remaining assets after we have paid all of our senior indebtedness in full.

The notes are obligations only of Financial Institutions, Inc. and not obligations of the Bank or any of our other subsidiaries and will be effectively subordinated to the existing and future indebtedness, deposits and other liabilities of the Bank and our other subsidiaries.

The notes are obligations solely of Financial Institutions, Inc. and are not obligations of the Bank or any of our other subsidiaries. The Bank and our other subsidiaries are separate and distinct legal entities from Financial Institutions, Inc. The rights of Financial Institutions, Inc. and the rights of its creditors, including the holders of the notes, to participate in any distribution of the assets of the Bank or any other subsidiary (either as a shareholder or as a creditor) upon an insolvency, bankruptcy, liquidation, dissolution, winding up or similar proceeding of the Bank or such other subsidiary (and the consequent right of the holders of the notes to participate in those assets after repayment of our existing or future senior indebtedness), will be subject to the claims of the creditors of the Bank, including depositors of the Bank or such other subsidiaries. Accordingly, the notes are effectively subordinated to all of the existing and future indebtedness, deposits and other liabilities of the Bank and our other subsidiaries, to the extent that those liabilities, including deposit liabilities, equal or exceed their respective assets. The notes do not limit the amount of indebtedness or other liabilities that the Bank or any of our other subsidiaries may incur, all of which would rank structurally senior to the notes. Any additional indebtedness and liabilities that our subsidiaries, including the Bank, incur may adversely affect our ability to pay our obligations on the notes.

The notes include limited covenants and do not restrict our ability to incur additional debt.

The notes do not contain any financial covenants that would require us to achieve or maintain any minimum financial results relating to our financial condition, liquidity or results of operations, to meet or exceed certain financial ratios as a general matter or to incur additional indebtedness or obligations or to maintain any reserves. Moreover, except under certain limited circumstances, the notes do not contain any covenants prohibiting or limiting us or our subsidiaries from granting liens on assets to secure indebtedness or other obligations, repurchasing our stock or other securities, including any of the notes, or paying dividends or making other distributions to our shareholders. The notes do not contain any provision that would provide protection to the holders of the notes against a material decline in our credit quality.

In addition, the notes do not limit the amount of additional indebtedness that we, the Bank or any of our other subsidiaries may incur or the amount of other obligations that we or the Bank may incur ranking senior or equal to the indebtedness evidenced by the notes. The issuance or guarantee of any such securities or the incurrence of any such other liabilities may reduce the amount, if any, recoverable by holders of the notes in the event of our insolvency, bankruptcy, liquidation, dissolution, winding up or similar proceeding and may limit our ability to meet our obligations under the notes.

To service our debt, we will require a significant amount of cash. Our ability to generate cash depends on many factors.

Our ability to make payments on or to refinance our indebtedness, including our ability to meet our obligations under the notes, and to fund our operations depends on our ability to generate cash and may depend

on our access to the capital markets. This will depend on our financial and operating performance, which is subject to general economic, financial, competitive, legislative, regulatory and capital market conditions that are beyond our control. If our cash flows and capital resources are insufficient to fund our debt service obligations, we may be unable to obtain new financing or to fund our obligations to our customers and business partners, implement our business plans, sell assets, seek additional capital or restructure or refinance our indebtedness, including the notes. As a result, we may be unable to meet our obligations under the notes. In the absence of sufficient capital resources, we could face substantial liquidity problems and might be required to dispose of material assets or operations to meet debt service and other obligations. We may not be able to consummate those dispositions of assets or obtain the proceeds that we could realize from them, and these proceeds may not be adequate to meet any debt service obligations then due, including obligations under the notes. Additionally, our ability to service our debt is dependent, in part, on the receipt of dividends paid to us by the Bank. The Bank is a separate legal entity that is legally distinct from us and has no obligation to make funds available to us for payments of principal of or interest on the notes. While we expect payments from the Bank to continue in the future, there are regulatory limits on the amount of dividends and distributions that the Bank can pay to us without regulatory approval. Accordingly, we can provide no assurance that we will receive dividends or other distributions from the Bank in an amount sufficient to pay the principal of or interest on the notes. See “Note (13.) Regulatory Matters” in the notes to our financial statements in our Annual Report on Form 10-K for the year ended December 31, 2024 for additional information.

Our indebtedness could adversely affect our financial results and prevent us from fulfilling our obligations under the notes.

In addition to our currently outstanding indebtedness, we may be able to borrow substantial additional indebtedness in the future. If new indebtedness is incurred in addition to our current debt levels, the related risks that we now face could increase. Our indebtedness, including the indebtedness we may incur in the future, could have important consequences for the holders of the notes, including:

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limiting our ability to satisfy our obligations with respect to the notes;

•

increasing our vulnerability to general adverse economic conditions;

•

limiting our ability to obtain additional financing to fund future working capital, capital expenditures and other general corporate requirements;

•

requiring a substantial portion of our cash flows from operations for the payment of principal of and interest on our indebtedness and thereby reducing our ability to use our cash flows to fund working capital, capital expenditures and general corporate requirements;

•

limiting our flexibility in planning for, or reacting to, changes in our business and the industry; and

•

putting us at a disadvantage compared to competitors with less indebtedness.

Regulatory guidelines may restrict our ability to pay the principal of and accrued and unpaid interest on, the notes, regardless of whether we are the subject of an insolvency proceeding.

As a bank holding company, our ability to pay the principal of, and interest on, the notes is subject to the rules and guidelines of the Federal Reserve regarding capital adequacy. We intend to treat the notes as “Tier 2 capital” under these rules and guidelines. The Federal Reserve guidelines generally require us to review the effects of the cash payment of Tier 2 capital instruments, such as the notes, on our overall financial condition. The guidelines also require that we review our net income for the current and past four quarters, and the amounts we have paid on Tier 2 capital instruments for those periods, as well as our projected rate of earnings retention. Moreover, pursuant to federal law and the Federal Reserve regulations, as a bank holding company, we are required to act as a source of financial and managerial strength to the Bank and commit resources to its support, including the guarantee of its capital plans if it becomes undercapitalized. Such support may be required at times when we may not otherwise be inclined or able to provide it. As a result of the foregoing, we may be unable to pay accrued interest on the notes on one or more of the scheduled interest payment dates, or at any other time, or the principal of the notes at the maturity of the notes.

If we were to be the subject of a bankruptcy proceeding under Chapter 11 of the U.S. Bankruptcy Code, the bankruptcy trustee would be deemed to have assumed, and would be required to cure, immediately any deficit under any commitment we have to any of the federal banking agencies to maintain the capital of the Bank, and any other insured depository institution for which we have such a responsibility, and any claim for breach of such obligation would generally have priority over most other unsecured claims.

Government regulation may affect the priority of the notes in the case of a bankruptcy or liquidation.

The Dodd-Frank Wall Street Reform Act (the “Dodd-Frank Act”) created a resolution regime known as the “orderly liquidation authority,” which may apply to us as a bank holding company. Under the orderly liquidation authority, the Federal Deposit Insurance Corporation may be appointed as receiver for an entity to liquidate the entity if the Secretary of the Treasury determines that the entity is in severe financial distress and that the entity’s failure would have serious adverse effects on the U.S. financial system.

If the FDIC is appointed as receiver under the orderly liquidation authority, then the Dodd-Frank Act, rather than applicable insolvency laws, would determine the powers of the receiver, and the rights and obligations of creditors and other parties who have dealt with the institution. There are substantial differences in the rights of creditors under the orderly liquidation authority compared to those under the U.S. Bankruptcy Code, including the right of the FDIC to disregard the strict priority of creditor claims in some circumstances, the use of an administrative claims procedure to determine creditors’ claims (as opposed to the judicial procedure utilized in bankruptcy proceedings) and the right of the FDIC to transfer claims to a “bridge” entity. As a consequence of the rights of the FDIC under the orderly liquidation authority, the holders of the notes may be fully subordinated to interests held by the U.S. government if we enter into a receivership, insolvency, liquidation or similar proceeding. While the FDIC has issued regulations to implement the orderly liquidation authority, not all aspects of how the FDIC might exercise this authority are known and additional rulemakings are possible. Further, it is uncertain how the FDIC might exercise its discretion under the orderly liquidation authority in a particular case.

Holders of the notes will have limited rights, including limited rights of acceleration, if there is an event of default.

Payment of principal on the notes may be accelerated only in the case of certain events of bankruptcy or insolvency involving us or the Bank. There is no automatic acceleration, or right of acceleration, in the case of default in the payment of principal of or interest on the notes, or in the performance of any of our other obligations under the notes or the indenture. Our regulators can, if we or the Bank become subject to an enforcement action, prohibit the Bank from paying dividends to us, and prevent payment of interest or principal on the notes and any dividends on our capital stock, but such limits will not permit acceleration of the notes. See “Description of the Notes—Events of Default; Right of Acceleration; Failure to Pay Principal or Interest.”

The amount of interest payable on the notes will vary beginning on December 15, 2030, and interest after that date may be less than the initial fixed annual interest rate of 6.50% before that date.

The interest rate on the notes will vary beginning on December 15, 2030, at a floating rate equal to the Floating Interest Rate (as defined below in “Description of the Notes—Principal, Maturity and Interest”), as determined quarterly on the determination date for the applicable interest period, plus 312 basis points. The interest rate that is determined on the relevant determination date will apply to the entire interest period following such determination date, even if the Floating Interest Rate changes during that interest period. The floating rate may be volatile over time and could be substantially less than the fixed interest rate we will pay before December 15, 2030. As a result, holders of the notes could experience a decline in their receipt of interest and the market price of the notes could decline. We have no control over a number of matters that may impact prevailing interest rates, including, without limitation, economic, financial, and political events that are important in determining the existence, magnitude, and longevity of market volatility, and other risks and their impact on the value of, or payments made on, the notes. In recent years, interest rates have been volatile, and that volatility may be expected in the future.

Because the notes may be prepaid at our option under certain circumstances before their maturity, you may be subject to reinvestment risk.

Subject to the prior approval of the Federal Reserve (or, as and if applicable, the rules of any appropriate successor bank regulatory agency), to the extent that such approval is then required under applicable laws or regulations, including capital regulations, we may prepay the notes at our option in whole or in part on or after December 15, 2030. In addition, at any time at which any notes remain outstanding, subject to the prior approval of the Federal Reserve (or, as and if applicable, the rules of any appropriate successor bank regulatory agency), to the extent that such approval is then required under applicable laws or regulations, including capital regulations, we may prepay the notes in whole or in part upon the occurrence of (1) a “Tier 2 Capital Event,” (2) a “Tax Event” or (3) an “Investment Company Event.” If we prepay the notes, holders of the notes will receive only the principal amount of the notes plus any accrued and unpaid interest to, but excluding, such prepayment date. If a full prepayment occurs, holders of the notes will not have the opportunity to continue to accrue and be paid interest to the Maturity Date. Any such prepayment may reduce the income or return that you may receive on an investment in the notes by reducing the term of the investment. If this occurs, you may not be able to reinvest the proceeds at an interest rate comparable to the rate paid on the notes.

Investors should not expect us to prepay the notes on or after the date on which they become prepayable at our option. Under Federal Reserve regulations, unless the Federal Reserve authorizes us in writing to do otherwise, we may not prepay the notes unless they are replaced with other Tier 2 capital instruments or unless we can demonstrate to the satisfaction of the Federal Reserve that, following prepayment, we will continue to hold capital commensurate with our risk.

Your ability to transfer the notes may be limited by the absence of an active trading market, and there is no assurance that any active trading market will develop for the notes.

The notes are a new issue of securities for which there is no established trading market, and we do not intend to apply for listing of the notes on any securities exchange or for quotation of the notes on a quotation system following registration of the notes pursuant to the terms of the registration rights agreements. In addition, the liquidity of any trading market for the notes, if any, will depend upon, among other things, the number of holders of the notes, our performance and prospects, the market for similar securities, the interest of securities dealers in making a market in the notes and other factors. As a result, we cannot provide you with any assurance regarding whether a trading market for the notes will develop or the ability of holders of the notes to sell their notes.

You should not rely on indicative or historical data concerning SOFR.

The interest rate during the floating rate period will be determined using Three-Month Term SOFR (unless a Benchmark Transition Event and its related Benchmark Replacement Date occur with respect to Three-Month Term SOFR, in which case the rate of interest will be based on the next-available Benchmark Replacement). In the following discussion of the Secured Overnight Financing Rate, or SOFR, when we refer to SOFR-linked notes, we mean the notes at any time when the interest rate on the notes is or will be determined based on SOFR, including Three-Month Term SOFR.

SOFR is calculated and published by the Federal Reserve Bank of New York (“FRBNY”) and is intended to be a broad measure of the cost of borrowing cash overnight collateralized by U.S. Treasury securities. FRBNY reports that SOFR includes all trades in the Broad General Collateral Rate, plus bilateral U.S. Treasury repurchase agreement, or repo, transactions cleared through the delivery-versus-payment service offered by the Fixed Income Clearing Corporation, or FICC, a subsidiary of the DTC. SOFR is filtered by FRBNY to remove a portion of the foregoing transactions considered to be “specials.” According to FRBNY, “specials” are repos for specific-issue collateral that take place at cash-lending rates below those for general collateral repos because cash providers are willing to accept a lesser return on their cash to obtain a particular security.

SOFR was selected as the preferred overnight reference rate for U.S. dollar financial contracts by the Alternative Reference Rates Committee (the “ARRC”). On July 29, 2021, the ARRC formally recommended the use of the CME Group’s forward-looking SOFR term rates. The CME Term SOFR reference rates provide forward-looking term rate estimates derived from SOFR, calculated and published for One-Month, Three-Month, Six-Month and Twelve-Month tenors (referred to as Term SOFR).

The benchmark rate applicable to the notes during the floating rate period commencing on December 15, 2030 is expected to be the then-current Three-Month Term SOFR, plus 312 basis points. Although the Three-Month Term SOFR is linked to SOFR, the Three-Month Term SOFR is calculated by the CME Group and not the FRBNY using transaction data from thirteen consecutive SR1 futures (1-month CME SOFR futures contracts) and five SR3 futures (3-month CME SOFR futures contracts). The Three-Month SOFR is underpinned by SR3 contracts with additional volumes from SR1 helping where available, as SR3 are the replacement contracts for Eurodollar futures. A set of volume weighted average prices are calculated using transaction prices observed during several observation intervals throughout the trading day. These are then used in a projection model to determine Term SOFR reference rates, including the Three-Month Term SOFR.

Term SOFR and SOFR may be more volatile than other benchmark or market rates.

Since the initial publication of SOFR, daily changes in the rate have, on occasion, been more volatile than daily changes in comparable benchmark or market rates, and SOFR and Term SOFR over time may bear little or no relation to the historical actual or historical indicative data. In addition, the return on and value of the Term SOFR-linked notes may fluctuate more than floating rate securities that are linked to less volatile rates.

Changes in the calculation of Term SOFR could adversely affect the amount of interest that accrues on the notes and the trading prices for the notes.

Because Term SOFR and SOFR are calculated based on data received from other sources, we have no control over its determination, calculation or publication. There can be no assurance that Term SOFR and SOFR will not be discontinued or fundamentally altered in a manner that is materially adverse to the interests of investors in the Term SOFR-linked notes. If the manner in which Term SOFR or SOFR is calculated is changed, that change may result in a change in the amount of interest that accrues on the Term SOFR-linked notes, which may adversely affect the trading prices of the Term SOFR-linked notes. Further, if the Benchmark rate on the Term SOFR-linked notes during the Floating Rate Period for any interest period declines to zero or becomes negative, then interest will only accrue on the Term SOFR linked notes at a rate equal to the spread of 312 basis points per annum with respect to that interest period. There is no assurance that changes in Term SOFR could not have a material adverse effect on the yield on, value of and market for the Term SOFR-linked notes.

We will act as the initial calculation agent and may have economic interests adverse to the interests of the holders of the notes.

We will act as the initial calculation agent, and we may continue to serve as calculation agent during the floating rate period. The calculation agent will make certain determinations, decisions or elections with respect to the interest rate during the floating rate period. Any exercise of discretion by us under the terms of the notes, including, without limitation, any discretion exercised by us acting as calculation agent, could present a conflict of interest. In making the required determinations, decisions and elections, we may have economic interests that are adverse to the interests of the holders of the notes, and those determinations, decisions or elections could have a material adverse effect on the yield on, value of and market for the notes. Any determination by us, as the calculation agent, or any other calculation agent appointed by us, will be conclusive and binding absent manifest error.

The market value of the notes may be less than the principal amount of the notes.

If a market develops for the notes, the prices at which holders may be able to sell their notes may be affected, potentially adversely, by a number of factors. These factors include: the method of calculating the

principal, premium, if any, interest or other amounts payable, if any, on the notes; the time remaining to maturity of the notes; the ranking of the notes; the aggregate amount outstanding of the notes; any prepayment or repayment features of the notes; any changes in the ratings on the notes provided by any rating agency; the prevailing interest rates being paid by other companies similar to us; the level, direction, and volatility of market interest rates generally; general economic conditions of the capital markets in the United States; geopolitical conditions and other financial, political, regulatory, and judicial events that affect the capital markets generally; the extent of any market-making activities, if any, with respect to the notes; and the operating performance of the Bank. Often, the only way to liquidate your investment in the notes before maturity will be to sell the notes. At that time, there may be a very illiquid market for the notes or no market at all.

Our credit ratings may not reflect all risks of an investment in the notes, and changes in our credit ratings may adversely affect your investment in the notes.

The credit ratings of our indebtedness are an assessment by rating agencies of our ability to pay our debts when due. These ratings are not recommendations to purchase, hold or sell the notes, inasmuch as the ratings do not comment as to market price or suitability for a particular investor, are limited in scope, and do not address all material risks relating to an investment in the notes, but rather reflect only the view of each rating agency at the time the rating is issued. The ratings are based on current and historical information furnished to the rating agencies by us and information obtained by the rating agencies from other sources, including financial strength, as well as factors not entirely within our control, such as conditions affecting the financial services industry generally. An explanation of the significance of such rating may be obtained from such rating agency. There can be no assurance that such credit ratings will remain in effect for any given period of time, or that such ratings will not be lowered, suspended or withdrawn entirely by the rating agencies, if, in each rating agency’s judgment, circumstances so warrant.

The credit ratings assigned to the notes may not reflect the potential impact of all risks related to structure and other factors on any trading market for, or trading value of, the notes. Ratings downgrades by a rating agency could have a significant and immediate impact on our funding and liquidity through cash obligations, reduced funding capacity and collateral triggers. A reduction in our or our subsidiaries’ credit ratings could also increase our borrowing costs and limit access to the capital markets. Additionally, we could be adversely affected by a general, negative perception of financial institutions caused by the downgrade of other financial institutions. Any real or anticipated changes in our credit ratings will generally affect the trading market for, or the trading value of, the notes. Accordingly, you should consult your own financial and legal advisors as to the risks entailed in an investment in the notes and the suitability of investing in the notes in light of your particular circumstances.

The notes will not be obligations of, or insured or guaranteed by, the FDIC, any other governmental agency or any of our subsidiaries and will be structurally subordinated to all liabilities of our subsidiaries.

Your investment in the notes will not be a bank deposit and will not be insured or guaranteed by the FDIC, any other government agency, any public or private insurer or any of our subsidiaries. The notes are not savings accounts, deposits or other obligations of, nor guaranteed by, any of our subsidiaries. The notes will be structurally subordinated to all existing and future indebtedness and other liabilities and obligations of our subsidiaries, which means that creditors of our subsidiaries (including, in the case of the Bank, its depositors) generally will be paid from those subsidiaries’ assets before holders of the notes would have any claims to those assets. Even if we become a creditor of any of our subsidiaries, our rights as a creditor would be subordinate to any security interest in the assets of that subsidiary and any debt of that subsidiary senior to the debt held by us, and our rights could otherwise be subordinated to the rights of other creditors and depositors of that subsidiary. Furthermore, none of our subsidiaries is under any obligation to make payments to us, and any payments to us would depend on the earnings or financial condition of our subsidiaries and various business considerations. Statutory, contractual or other restrictions also limit our subsidiaries’ ability to pay dividends or make distributions, loans or advances to us. For these reasons, we may not have access to any assets or cash flows of our subsidiaries to make interest and principal payments on the notes. Your investment will be subject to investment risk, and you must be capable of affording the loss of your entire investment.

Some noteholders may be required to comply with the registration and prospectus delivery requirements of the Securities Act.

If you exchange your Old Notes in the exchange offer for the purpose of participating in a distribution of the New Notes, you may be deemed to have received restricted securities and, if so, you will be required to comply with the registration and prospectus delivery requirements of the Securities Act in connection with any resale transaction. In addition, any broker-dealer who holds Old Notes acquired for its own account as a result of market-making activities or other trading activities and who receives New Notes in exchange for such Old Notes pursuant to the exchange offer may be a statutory underwriter and must deliver a prospectus meeting the requirements of the Securities Act in connection with any resale of such New Notes. Our obligation to keep the registration statement of which this prospectus forms a part effective is limited. Accordingly, we cannot guarantee that a current prospectus will be available at all times to broker-dealers wishing to resell their New Notes.

There can be no assurance that the notes will qualify for the tax treatment for which the Company intends the notes to qualify.

Although the Company intends for the notes to qualify for tax treatment that is favorable to the Company, the Company has not sought advice from its accountants, nor has it sought a ruling from the U.S. Internal Revenue Service (the “IRS”), as to the federal income tax consequences of issuing the notes. There can be no assurance that upon future review, the Company’s accountants will determine that the notes do not qualify for the intended tax treatment. Similarly, there can be no assurance that the IRS will not successfully challenge the intended tax treatment of the notes. If at any time within the first five years after the issue date, the interest payable by the Company on the notes is not, or will not be, deductible by the Company, in whole or in part, for federal income tax purposes, we may prepay the notes in whole or in part, and without premium or penalty.

USE OF PROCEEDS

The exchange offer is intended to satisfy our obligations under the registration rights agreements. We will not receive any cash proceeds from the issuance of the New Notes. In consideration for issuing the New Notes, we will receive an equal principal amount of the Old Notes. We will cancel all of the Old Notes that are tendered and accepted for exchange. Accordingly, no additional debt will result from the exchange offer. We have agreed to bear all expenses of the exchange offer.

THE EXCHANGE OFFER

General

In connection with the issuance of the Old Notes on December 11, 2025, we entered into registration rights agreements with the purchasers of the Old Notes. The registration rights agreements provide for the exchange offer we are making pursuant to this prospectus. The exchange offer will permit eligible holders of Old Notes to exchange their Old Notes for New Notes that are identical in all material respects with the Old Notes, except that:

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the New Notes have been registered with the SEC under the Securities Act and, as a result, will not bear any legend restricting their transfer;

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the New Notes bear different CUSIP numbers from the Old Notes;

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the New Notes generally will not be subject to transfer restrictions;

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holders of the New Notes will not be entitled to registration rights under the registration rights agreements or otherwise; and

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because the New Notes will not be entitled to registration rights, holders of the New Notes will not have the right to additional interest under the circumstances described in the registration rights agreements relating to our fulfillment of our registration obligations.

The New Notes will evidence the same debt as the Old Notes, and holders of the New Notes will be entitled to the benefits of the indenture. Accordingly, the New Notes and the Old Notes will be treated as a single series of subordinated debt securities under the indenture. Any Old Notes that are not tendered and accepted for exchange in the exchange offer will remain outstanding, and interest on any such Old Notes will continue to accrue at the applicable interest rate and be subject to the terms of the indenture.

We intend to conduct the exchange offer in accordance with the provisions of the registration rights agreements, the applicable requirements of the Exchange Act, and the related rules and regulations of the SEC applicable to transactions of this type.

The exchange offer does not depend on any minimum aggregate principal amount of Old Notes being tendered for exchange.

We will be deemed to have accepted validly tendered Old Notes if and when we have given written notice to the exchange agent of our acceptance of such Old Notes. Subject to the terms and conditions of the exchange offer, delivery of New Notes will be made by the exchange agent promptly after receipt of our notice of acceptance. The exchange agent will act as agent for the holders of Old Notes tendering their Old Notes to receive New Notes from us in exchange for such tendered and accepted Old Notes. The exchange offer is subject to the conditions set forth below under “—Conditions.” As a result of these conditions (which may be waived by us, in whole or in part, in our absolute discretion), we may not be required to exchange any of the Old Notes. In such case, or if any tendered Old Notes are not accepted for exchange because of an invalid tender, the occurrence of other events described in this prospectus or otherwise, we will return or cause to be returned the Old Notes not exchanged to the tendering holder after the expiration or termination of the exchange offer.

If a holder of Old Notes validly tenders Old Notes in the exchange offer, the tendering holder will not be required to pay us brokerage commissions or fees. In addition, subject to the instructions in the letter of transmittal and certain limited exceptions described in this prospectus and the letter of transmittal, the tendering holder will not have to pay transfer taxes for the exchange of Old Notes. Subject to certain exceptions described in this prospectus, we will pay all of the expenses in connection with the exchange offer, other than certain applicable taxes. See “—Fees and Expenses.”

Holders of outstanding Old Notes do not have any appraisal, dissenters’ or similar rights in connection with the exchange offer. Any outstanding Old Notes that are not tendered, or are tendered but not accepted, in connection with the exchange offer will remain outstanding. See “Risk Factors—Risks Related to the Exchange Offer.

NEITHER WE NOR THE EXCHANGE AGENT NOR THE TRUSTEE ARE MAKING ANY RECOMMENDATION TO THE HOLDERS OF THE OUTSTANDING OLD NOTES AS TO WHETHER TO TENDER OR REFRAIN FROM TENDERING ALL OR ANY PORTION OF THEIR OUTSTANDING OLD NOTES IN THE EXCHANGE OFFER. IN ADDITION, NEITHER WE NOR THE EXCHANGE AGENT NOR THE TRUSTEE HAVE AUTHORIZED ANYONE TO MAKE ANY SUCH RECOMMENDATION. HOLDERS OF THE OUTSTANDING OLD NOTES MUST MAKE THEIR OWN DECISION WHETHER TO TENDER PURSUANT TO THE EXCHANGE OFFER, AND, IF SO, THE AGGREGATE PRINCIPAL AMOUNT OF OUTSTANDING OLD NOTES TO TENDER AFTER READING THIS PROSPECTUS AND THE LETTER OF TRANSMITTAL AND CONSULTING WITH THEIR ADVISERS, IF ANY, BASED ON THEIR FINANCIAL POSITION AND INDIVIDUAL REQUIREMENTS.

Registration Rights Agreements

We issued the Old Notes in a private placement exempt from the registration requirements under the Securities Act and applicable state securities laws. In connection with the issuance of the Old Notes, we entered into registration rights agreements with the purchasers of the Old Notes, and we are making the exchange offer to comply with our contractual obligations under the registration rights agreements.

The following provides a summary of certain terms of the registration rights agreements. This summary is qualified in its entirety by reference to the complete registration rights agreements, a form of which is incorporated by reference as an exhibit to the registration statement of which this prospectus is a part.

Under the terms of the registration rights agreement, we agreed to register the New Notes and undertake the exchange offer. The exchange offer is intended to satisfy the rights of holders of Old Notes under those registration rights agreements. After the exchange offer is completed, we will have no further obligations, except under the limited circumstances described below, to provide for any exchange or undertake any further registration with respect to the Old Notes.

Under the terms of the registration rights agreements, we agreed, among other things, to use commercially reasonable efforts to:

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file a registration statement with the SEC under the Securities Act on or before the 90^th day after December 11, 2025 with respect to a registered offer to exchange the Old Notes for substantially identical notes that do not contain transfer restrictions and will be registered under the Securities Act;

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cause that registration statement to become effective no later than 150 days after December 11, 2025;

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cause that registration to remain effective until the closing of the exchange offer; and

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commence the exchange offer promptly after the effectiveness of the registration statement and keep the exchange offer open for not less than 20 business days, or longer if required by applicable law, after the date on which notice of the exchange offer is given to the holders of the Old Notes; and

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consummate the exchange offer no later than 45 days after the effective date of that registration statement.

We also agreed to issue and exchange New Notes for all Old Notes duly tendered and not validly withdrawn before the expiration of the exchange offer. We are sending this prospectus, together with a letter of transmittal, to all the holders of the Old Notes known to us. For each Old Note validly tendered to us in the exchange offer and not validly withdrawn, the holder will receive a New Note having a principal amount equal to the principal amount of the tendered Old Note. Old Notes may be exchanged, and New Notes will be issued, only in minimum denominations of $100,000 and integral multiples of $1,000 in excess thereof.

We further agreed that under certain circumstances we would file a shelf registration statement with the SEC that would allow resales by certain holders of the Old Notes in lieu of such holders participating in the exchange offer.

Eligibility; Transferability

We are making the exchange offer in reliance on interpretations of the staff of the SEC set forth in several no-action letters provided to other parties. We have not sought or received our own no-action letter from the staff of the SEC with respect to this exchange offer and the related transactions, and there can be no assurance that the staff of the SEC will make a determination in the case of this exchange offer and such transactions that is similar to its determinations in the above mentioned no-action letters. However, based on these existing SEC staff interpretations, we believe that you, or any other person receiving New Notes, may offer for resale, resell or otherwise transfer the New Notes without complying with the registration and prospectus delivery requirements of the U.S. federal securities laws, provided that:

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you are not, nor is any such person, an “affiliate” of ours within the meaning of Rule 405 under the Securities Act;

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you are, or the person receiving the New Notes is, acquiring the New Notes in the ordinary course of business;

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you do not, nor does any such person, have an arrangement or understanding with any person to participate in any distribution (within the meaning of the Securities Act) of the New Notes;

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you are not, nor is any such person, a broker-dealer registered under the Exchange Act, and you are not engaged in and do not intend to engage in, nor is any such person engaged in or intending to engage in, any distribution (within the meaning of the Securities Act) of the New Notes; and

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you are not acting on behalf of any person who could not truthfully make these statements.

To participate in the exchange offer, you must represent as a holder of Old Notes that each of these statements is true.

In addition, for broker-dealers registered under the Exchange Act to participate in the exchange offer, each such broker-dealer must also: (1) represent that it is participating in the exchange offer for its own account and is exchanging Old Notes acquired as a result of market-making activities or other trading activities; (2) confirm that it has not entered into any arrangement or understanding with us or any of our affiliates to distribute the New Notes; and (3) acknowledge that it will deliver a prospectus meeting the requirements of the Securities Act in connection with any resale of the New Notes. The letter of transmittal to be delivered in connection with a tender of the Old Notes states that by acknowledging that it will deliver, and by delivering, a prospectus, a broker-dealer will not be deemed to admit that it is an “underwriter” within the meaning of the Securities Act. This prospectus, as it may be amended or supplemented from time to time, may be used by a broker-dealer in connection with resale of the New Notes received in exchange for the Old Notes where such Old Notes were acquired by such broker-dealer as a result of market-making activities or other trading activities. We have agreed that, for a period of 180 days following the expiration date, we will amend or supplement this prospectus to expedite or facilitate the disposition of any New Notes by such broker-dealers.

Any holder of Old Notes (1) who is our affiliate, (2) who does not acquire the New Notes in the ordinary course of business, (3) who participates in, or intends to participate in, the exchange offer for the purpose of, or with a view to, distributing the New Notes or (4) who is a broker-dealer who purchased the Old Notes directly from us:

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will not be able to rely on the interpretation of the staff of the SEC set forth in the no-action letters described above;

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will not be able to tender Old Notes in the exchange offer; and

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must comply with the registration and prospectus delivery requirements of the Securities Act in connection with any sale or transfer of the New Notes, unless the sale or transfer is made pursuant to an exemption from those requirements.

The exchange offer is not being made to, nor will we accept tenders for exchange from, holders of Old Notes in any jurisdiction in which the exchange offer or the acceptance of the exchange offer would not be in compliance with the securities or blue sky laws of such jurisdiction.

Expiration of the Exchange Offer; Extensions; Amendments

The exchange offer will expire at 5:00 p.m., Eastern Time, on [expiration date], or at such later date or time to which we may extend the exchange offer. We refer to such date, as it may be extended, as the expiration date. To extend the exchange offer, we will notify the exchange agent and each registered holder of the Old Notes of any extension before 9:00 a.m., Eastern Time, on the next business day after the previously scheduled expiration date. During any such extension, all Old Notes previously tendered will remain subject to the exchange offer and may be accepted for exchange by us.

We reserve the right to extend the exchange offer, delay accepting any tendered Old Notes or, if any of the conditions described below under the heading “Conditions” have not been satisfied, to terminate the exchange offer. We also reserve the right to amend the terms of the exchange offer in any manner. We will give written notice of any delay, extension or termination of, or amendment to, the exchange offer to the exchange agent. We will keep the exchange offer open for not less than 20 business days, or longer if required by applicable law, after the date on which notice of the exchange offer is given to holders of the Old Notes.

If we amend the exchange offer in a manner that we consider material, we will disclose that amendment by means of a prospectus supplement, and we will extend the exchange offer so that at least five business days remain in the exchange offer following notice of the material change.

If we determine to make a public announcement of any delay, extension, amendment or termination of the exchange offer, we will do so by making a timely release through an appropriate news agency.

If we terminate or withdraw the exchange offer, we will promptly pay the consideration offered, or return any Old Notes deposited, under the exchange offer as required by Rule 14e-1(c) under the Exchange Act.

Conditions

The exchange offer is not conditioned on any minimum aggregate principal amount of Old Notes being tendered or accepted for exchange. Notwithstanding any other term of the exchange offer, we will not be required to accept for exchange, or issue any New Notes for, any Old Notes and may terminate or amend the exchange offer before the acceptance of the Old Notes, if:

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such Old Notes are tendered to us other than in accordance with the terms and conditions of the exchange offer;

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we determine that the exchange offer, or the making of any exchange by a holder, violates any applicable law or any applicable interpretation by the staff of the SEC; or

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any action or proceeding is instituted or threatened in any court or by or before any governmental agency with respect to the exchange offer that, in our judgment, would reasonably be expected to impair our ability to proceed with the exchange offer.

The conditions listed above are for our sole benefit and may be asserted by us regardless of the circumstances giving rise to any of these conditions. We reserve the absolute right to waive these conditions in whole or in part at any time and from time to time in our sole discretion before the expiration date, subject to applicable law. Our failure at any time to exercise any of the above rights will not be considered a waiver of that right, and that right will be considered an ongoing right that we may assert at any time and from time to time.

In addition, we will not accept for exchange any Old Notes tendered, and no New Notes will be issued in exchange for those Old Notes, if at any time any stop order is threatened or issued by the SEC with respect to the registration statement for the exchange offer and the New Notes or the qualification of the indenture under the Trust Indenture Act of 1939, as amended (the “Trust Indenture Act’). In any such event, we must use our commercially reasonable efforts to obtain the withdrawal of any stop order as soon as practicable.

Further, we will not be obligated to accept for exchange the Old Notes of any holder that has not made to us the representations described under “—Eligibility; Transferability” and “Plan of Distribution.”

Procedures for Tendering Old Notes

To participate in the exchange offer, you must validly tender your Old Notes to the exchange agent as described below. It is your responsibility to validly tender your Old Notes.

If you have any questions or need help in exchanging your Old Notes, please call the exchange agent, whose address and phone number are set forth in “—Exchange Agent.”

Certain of the Old Notes were issued in book-entry form and are currently represented by global certificates held for the account of DTC. Accordingly, DTC will be the only entity that can tender those Old Notes for New Notes. Therefore, to tender Old Notes subject to the exchange offer and to obtain New Notes you must:

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comply with DTC’s ATOP procedures described below; and

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the exchange agent must receive a timely confirmation of a book-entry transfer of the Old Notes into its account at DTC through ATOP pursuant to the procedure for book-entry transfer described below, along with a properly transmitted “agent’s message” (as defined below), before the expiration date of the exchange offer.

Following receipt, the exchange agent will establish an ATOP account with DTC for purposes of the exchange offer promptly after the commencement of the exchange offer. Any financial institution that is a DTC participant, including your broker or bank, may make a book-entry tender of outstanding Old Notes by causing the book-entry transfer of such Old Notes into our ATOP account in accordance with DTC’s procedures for such transfers. In connection with the transfer, DTC must send an “agent’s message” to the exchange agent on or before 5:00 p.m., Eastern Time, on the expiration date of the exchange offer.

The term “agent’s message” means a message transmitted by the DTC participants to DTC, and thereafter transmitted by DTC to the exchange agent, which states that DTC has received an express acknowledgement from the participant stating that such participant and beneficial holder agree to be bound by the terms of the exchange offer, including the letter of transmittal, and that the agreement may be enforced against such participant.

Each agent’s message must include the following information:

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name of the beneficial owner tendering such Old Notes;

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account number of the beneficial owner tendering such Old Notes;

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principal amount of Old Notes tendered by such beneficial owner; and

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a confirmation that the beneficial owner of the Old Notes has made the representations for our benefit set forth under “Representations” below.

The delivery of the Old Notes through DTC, and any transmission of an agent’s message through ATOP, is at the election and risk of the person tendering Old Notes. If we do not accept any tendered Old Notes for exchange or if Old Notes are submitted for a greater principal amount than the holder desires to exchange, the unaccepted or non-exchanged Old Notes will be returned, without expense, to their tendering holder. Such non-exchanged Old Notes will be credited to an account maintained with DTC. These actions will occur promptly after the expiration or termination of the exchange offer.

The tender by a holder of Old Notes that is not validly withdrawn before the expiration date of the exchange offer and that is accepted by us will constitute a binding agreement between us and the holder in accordance with the terms and subject to the conditions set forth in this prospectus and in the accompanying letter of transmittal. By using the ATOP procedures to exchange Old Notes, you will not be required to deliver a letter of transmittal to the exchange agent. However, you will be bound by its terms, and you will be deemed to have made the acknowledgements and the representations and warranties it contains, just as if you had signed it.

Certain of the Old Notes were issued in physical (certificated) form to certain initial purchasers. Accordingly, such holders of Old Notes must physically tender their Old Notes for New Notes. To tender Old Notes in certificated form subject to the exchange offer and to obtain New Notes you must transmit to the exchange agent, at its address listed under “ Exchange Agent,” the following:

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the physical Old Note;

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a properly completed and duly executed letter of transmittal; and

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all other documents required by the letter of transmittal.

The tender by a holder of Old Notes represented in physical form that is not validly withdrawn before the expiration date of the exchange offer and that is accepted by us will constitute a binding agreement between us and the holder in accordance with the terms and subject to the conditions set forth in this prospectus and in the accompanying letter of transmittal. You will be required to deliver the physical note and a letter of transmittal to the exchange agent and will be bound by the letter of transmittal terms.

There is no procedure for guaranteed late delivery of the Old Notes in connection with the exchange offer.

We will determine all questions as to the validity, form, eligibility (including time of receipt) and acceptance and withdrawal of tendered Old Notes in our sole discretion. We reserve the absolute right to reject any and all Old Notes not properly tendered or any Old Notes whose acceptance by us would, in the opinion of our counsel, be unlawful. We also reserve the right to waive any defects, irregularities or conditions of tender as to any particular Old Notes either before or after the expiration date. Our interpretation of the terms and conditions of the exchange offer (including the instructions in the accompanying letter of transmittal) will be final and binding on all parties. Unless waived, any defects or irregularities in connection with tenders of Old Notes must be cured within a time period we will reasonably determine. Although we intend to request the exchange agent to notify holders of defects or irregularities relating to tenders of Old Notes, neither we, the exchange agent nor any other person will have any duty or incur any liability for failure to give such notification. Tenders of Old Notes will not be considered to have been made until such defects or irregularities have been

cured or waived. If we waive any terms or conditions with respect to a noteholder, we will extend the same waiver to all noteholders with respect to that term or condition. Any Old Notes received by the exchange agent that are not validly tendered and as to which the defects or irregularities have not been cured or waived will be returned by the exchange agent, without expense, to the tendering holders, unless otherwise provided in the accompanying letter of transmittal, promptly following the expiration date of the exchange offer.

Representations

By tendering Old Notes, each holder is deemed to have represented to us all of the representations contained in the letter of transmittal, including that:

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any New Notes that you receive will be acquired in the ordinary course of business;

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you are not participating in the exchange offer with a view to distribute any New Notes nor do you have any arrangement or understanding with any person to participate in the distribution (within the meaning of the Securities Act) of the New Notes in violation of the provisions of the Securities Act;

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you are not an “affiliate” (within the meaning of Rule 405 under the Securities Act);

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if you are a broker-dealer that will receive New Notes for your own account in exchange for Old Notes, you acquired those New Notes as a result of market-making or other trading activities and you will deliver a prospectus (or to the extent permitted by law, make available a prospectus to purchasers) in connection with any resale of such New Notes; and

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you are not acting on behalf of any person or entity who could not truthfully make the foregoing representations and warranties.

Proper Execution and Delivery of Letter of Transmittal

Generally, an eligible institution must guarantee signatures on a letter of transmittal or notice of withdrawal unless:

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you tender your Old Notes as the registered holder and the New Notes issued in exchange for your Old Notes are to be issued in your name and delivered to you at your registered address appearing on the security register for the Old Notes; or

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you tender your Old Notes for the account of an eligible institution.

For the purposes of this prospectus, an “eligible institution” means an “eligible guarantor institution” as defined by Rule 17Ad-15 under the Exchange Act that is a member of a recognized signature guarantee program (i.e., Securities Transfer Agents Medallion Program, Stock Exchange Medallion Program or New York Stock Exchange Medallion Signature Program).

If the letter of transmittal is signed by the holder(s) of Old Notes tendered thereby, the signature(s) must correspond with the name(s) as written on the face of the Old Notes without alteration, enlargement or any change whatsoever. If any of the Old Notes tendered are held by two or more holders, all such holders must sign the letter of transmittal. If any of the Old Notes tendered thereby are registered in different names on different Old Notes, it will be necessary to complete, sign and submit as many separate letters of transmittal, and any accompanying documents, as there are different registrations of certificates.

If Old Notes that are not tendered for exchange under the exchange offer are to be returned to a person other than the holder thereof, certificates for such Old Notes must be endorsed or accompanied by an appropriate instrument of transfer, signed exactly as the name of the registered owner appears on the certificates, with the signatures on the certificates or instruments of transfer guaranteed by an eligible institution.

If the letter of transmittal is signed by a person other than the holder of any Old Notes listed therein, those Old Notes must be properly endorsed or accompanied by a properly completed bond power, signed by such holder exactly as such holder’s name appears on such Old Notes. If the letter of transmittal or any Old Notes, bond powers or other instruments of transfer are signed by trustees, executors, administrators, guardians, attorneys-in-fact, officers of corporations or others acting in a fiduciary or representative capacity, those persons should so indicate when signing, and, unless waived by us, evidence satisfactory to us of their authority to so act must be submitted with the letter of transmittal.

No alternative, conditional, irregular or contingent tenders will be accepted. By executing the letter of transmittal (or facsimile thereof), the tendering holders of Old Notes waive any right to receive any notice of the acceptance for exchange of their Old Notes. Tendering holders should indicate in the applicable box in the letter of transmittal the name and address to which payments and/or substitute certificates evidencing Old Notes for amounts not tendered or not exchanged are to be issued or sent, if different from the name and address of the person signing the letter of transmittal. If no such instructions are given, Old Notes not tendered or exchanged will be returned to the tendering holder.

All questions as to the validity, form, eligibility (including time of receipt), and acceptance and withdrawal of tendered Old Notes will be determined by us in our absolute discretion, which determination will be final and binding. We reserve the absolute right to reject any and all tendered Old Notes determined by us not to be in proper form or not to be properly tendered or any tendered Old Notes our acceptance of which would, in the opinion of our counsel, be unlawful. We also reserve the right to waive, in our absolute discretion, any defects, irregularities or conditions of tender as to particular Old Notes, whether or not waived in the case of other Old Notes. Our interpretation of the terms and conditions of the exchange offer (including the instructions in the letter of transmittal) will be final and binding on all parties. Unless waived, any defects or irregularities in connection with tenders of Old Notes must be cured within such time as we will determine. Although we intend to notify holders of defects or irregularities with respect to tenders of Old Notes, neither we, the exchange agent nor any other person will be under any duty to give such notification or will incur any liability for failure to give any such notification. Tenders of Old Notes will not be deemed to have been made until such defects or irregularities have been cured or waived. Any holder whose Old Notes have been mutilated, lost, stolen or destroyed will be responsible for obtaining replacement securities or for arranging for indemnification with the trustee of the Old Notes. Holders may contact the exchange agent for assistance with these matters.

Withdrawal of Tenders

Except as otherwise provided in this prospectus, you may validly withdraw your tender of Old Notes at any time before 5:00 p.m., Eastern Time, on the expiration date of the exchange offer. For a withdrawal of Old Notes represented by global certificates to be effective, you must comply with the appropriate procedures of DTC’s ATOP system before 5:00 p.m., Eastern Time, on the expiration date of the exchange offer. Any such notice of withdrawal must:

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specify the name of the tendering holder of Old Notes;

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specify the principal amount of the Old Notes delivered for exchange;

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specify the name and number of the account at DTC to be credited with the withdrawn Old Notes; and

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include a statement that such holder is withdrawing its election to have such Old Notes exchanged.

For a withdrawal of Old Notes represented by physical certificates to be effective, the exchange agent must receive a written notice of withdrawal before 5:00 p.m., Eastern Time, on the expiration date of the exchange offer. Any such notice of withdrawal must:

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specify the name of the tendering holder of Old Notes;

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specify the principal amount of the Old Notes delivered for exchange; and

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include a statement that such holder is withdrawing its election to have such Old Notes exchanged.

We will determine all questions as to the validity, form and eligibility (including time of receipt) of such withdrawal notices. Any Old Notes so withdrawn will be considered not to have been validly tendered for purposes of the applicable exchange offer, and no New Notes will be issued in exchange for such Old Notes unless the Old Notes withdrawn are validly re-tendered. Validly withdrawn Old Notes may be re-tendered by following one of the procedures described above under “—Procedures for Tendering Old Notes” at any time before the expiration date of the exchange offer.

Exchange Agent

Wilmington Trust, National Association has been appointed the exchange agent for the exchange offer. Wilmington Trust, National Association is also the trustee under the indenture. Letters of transmittal, any original certificated notes, and all correspondence in connection with the exchange offer should be sent or delivered by each holder of Old Notes, or a beneficial owner’s commercial bank, broker, dealer, trust company or other nominee, to the exchange agent as follows:

By Hand, Overnight Delivery or Mail (Registered or Certified Mail Recommended):

Wilmington Trust, National Association

Attn: Workflow Management – 5^th Floor

1100 North Market Street

Wilmington, DE 19890-1626

The method of delivery for original notes, letters of transmittal and all other required documents is at the holder’s election and risk. Holders of certificated Old Notes should not send original notes, letters of transmittal or other required documents to the Company. Any Old Notes which have been tendered but which are not accepted for exchange or which are withdrawn will be returned to the holder, without expense to such holder, promptly after withdrawal, rejection of tender or termination of the applicable exchange offer.

For additional information, you may contact the exchange agent by emailing DL-DTC-Transfer_Agent_Team@mtb.com.

We will pay the exchange agent reasonable and customary fees for its services (including attorneys’ fees) and will reimburse it for its reasonable out-of-pocket expenses in connection with the exchange offer.

Fees and Expenses

We will bear the expenses of soliciting tenders of the Old Notes and issuance of the New Notes. The principal solicitation is being made by mail. However, we may make additional solicitations by email, telephone or in person by our officers and employees and those of our affiliates.

We have not retained any dealer-manager in connection with the exchange offer and will not make any payments to broker-dealers or others soliciting acceptances of the exchange offer. As indicated above, we will, however, pay the exchange agent reasonable and customary fees for its services and reimburse it for its related reasonable out-of-pocket expenses. We will also pay any other cash expenses that we incur in connection with the exchange offer.

Except as described below, we will pay all transfer taxes, if any, applicable to the exchange of Old Notes under the exchange offer. The tendering holder will be required to pay any transfer taxes, whether imposed on the registered holder or any other person, if:

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New Notes and/or substitute Old Notes not exchanged are to be delivered to, or registered or issued in the name of, any person other than the registered holder of the Old Notes so exchanged;

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tendered Old Notes are registered in the name of any person other than the person signing the letter of transmittal; or

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a transfer tax is imposed for any reason other than the exchange of Old Notes under the exchange offer.

If satisfactory evidence of payment of transfer taxes is not submitted with the letter of transmittal, the amount of any transfer taxes will be billed to the tendering holder.

Accounting Treatment

We will record the New Notes at the same carrying value as the Old Notes reflected in our accounting records on the date of the exchange. Accordingly, we will not recognize any gain or loss for accounting purposes upon completion of the exchange offer.

Consequences of Failure to Exchange

Old Notes that are not exchanged will be subject to the restrictions on transfer described in the Old Notes.

Accordingly, such Old Notes may not be offered, sold, pledged or otherwise transferred except:

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to us or to any of our subsidiaries;

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under a registration statement that has been declared effective under the Securities Act;

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for so long as the Old Notes are eligible for resale pursuant to Rule 144A under the Securities Act, to a person the holder of the Old Notes and any person acting on its behalf reasonably believes is a “qualified institutional buyer” as defined in Rule 144A, that purchases for its own account or for the account of another qualified institutional buyer, in each case to whom notice is given that the transfer is being made in reliance on Rule 144A; or

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under any other available exemption from the registration requirements of the Securities Act (in which case we and the trustee shall have the right to require the delivery of an opinion of counsel (at the holder’s sole cost), certifications and/or other information satisfactory to us and the trustee);

in each case subject to compliance with any applicable foreign, state or other securities laws.

Upon completion of the exchange offer, due to the restrictions on transfer of the Old Notes and the absence of such restrictions applicable to the New Notes, it is likely that the market, if any, for Old Notes will be relatively less liquid than the market for New Notes. Consequently, holders of Old Notes who do not participate in the exchange offer could experience significant diminution in the value of their Old Notes, compared to the value of the New Notes. The holders of Old Notes not tendered will have no further registration rights, except that, under limited circumstances specified in the registration rights agreements, we may be required to file a shelf registration statement for a continuous offer of Old Notes.

Additional Information Regarding the Registration Rights Agreements

As noted above, we are effecting the exchange offer to comply with our contractual obligations under the registration rights agreements. The registration rights agreements require us to cause an exchange offer registration statement to be filed with the SEC under the Securities Act, use our commercially reasonable efforts to cause the registration statement to become effective, and satisfy certain other obligations, within certain time periods.

If:

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the registration statement is not filed with the SEC on or before the 90^th day after December 11, 2025;

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the registration statement is not declared effective by the SEC on or before the 150^th day after December 11, 2025;

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the exchange offer is not consummated within 45 days following the effective date of the registration statement;

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if required, a shelf registration statement is not filed with the SEC on or before (A) the 180^th day following December 11, 2025 or (B) the 60^th day after the obligation to file a shelf registration statement with the SEC arises, whichever is later;

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if required, a shelf registration statement is not effective on or before (A) the 225^th day following December 11, 2025 or (B) the 105^th day after an obligation to file with the SEC a shelf registration statement arises, whichever is later;

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a shelf registration statement is effective with the SEC but such shelf registration statement ceases to be effective or such shelf registration statement or the prospectus included therein ceases to be usable in connection with resales of the registrable securities for any act or omission of the Company and (A) the aggregate number of days in any consecutive 365-day period for which the shelf registration statement or such prospectus shall not be effective or usable exceeds 120 days, (B) the shelf registration statement or such prospectus shall not be effective or usable for more than two periods (regardless of duration) in any consecutive 365-day period, or (C) the shelf registration statement or such prospectus shall not be effective or usable for a period of more than 90 consecutive days; or

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the registration statement is effective with the SEC but, if the registration statement is being used in connection with the resale of the New Notes, the registration statement ceases to be effective or the registration statement or the prospectus included therein ceases to be usable in connection with resales of New Notes due to any act or omission of the Company during the 180-day period following the last date on which exchanges are accepted and (A) the aggregate number of days in any consecutive 365-day period for which the registration statement or such prospectus shall not be effective or usable exceeds 120 days, (B) the registration statement or such prospectus shall not be effective or usable for more than two periods (regardless of duration) in any consecutive 365-day period, or (C) the registration statement or the prospectus shall not be effective or usable for a period of more than 90 consecutive days;

the interest rate on the Old Notes will be increased by 0.25% per annum immediately following the applicable date of such registration default and will increase by an additional 0.25% per annum immediately following each 90-day period during which additional interest accrues, but in no event will such increase exceed 0.50% per annum. If at any time more than one registration default has occurred and is continuing, the increase in interest rate will apply as if there occurred a single registration default that begins on the date that the earliest such registration default occurred and ends on such date that there is no registration default. Following the cure of all such registration defaults, the accrual of additional interest will cease and the interest rate will be reduced to the original interest rate borne by the Old Notes.

Our obligation to register the New Notes will terminate upon completion of the exchange offer. However, under certain limited circumstances specified in the registration rights agreements, we may be required to file a shelf registration statement for a continuous offer in connection with the Old Notes.

DESCRIPTION OF THE NOTES

On December 11, 2025, we issued $80.0 million in aggregate principal amount of our 6.50% Fixed-to-Floating Rate Subordinated Notes due 2035, which we refer to in this prospectus as the “Old Notes.” The Old Notes were issued in a private placement transaction to certain qualified institutional buyers, and as such, were not registered under the Securities Act. The Old Notes were issued under an indenture, dated

December 11, 2025, between Financial Institutions, Inc., as issuer, and Wilmington Trust, National Association, as trustee, which we refer to as the “indenture.” The term “notes” refers collectively to the Old Notes and the New Notes.

The New Notes will be issued under the indenture and will evidence the same debt as the Old Notes. The terms of the New Notes are identical in all material respects to those of the Old Notes, except that:

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the New Notes have been registered with the SEC under the Securities Act and, as a result, will not bear any legend restricting their transfer;

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the New Notes bear a different CUSIP number from the Old Notes;

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the New Notes are generally not subject to transfer restrictions;

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holders of the New Notes are not entitled to registration rights under the registration rights agreements that we entered into with the initial purchasers of the Old Notes or otherwise; and

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because the New Notes will not be entitled to registration rights, holders of the New Notes will not have the right to additional interest under the circumstances described in the registration rights agreement relating to our fulfillment of our registration obligations.

The New Notes will be issued only in registered form without coupons and in minimum denominations of $100,000 and any integral multiple of $1,000 in excess thereof. Unless otherwise required for accredited investors, the New Notes will be evidenced by a global note deposited with the trustee for the New Notes, as custodian for DTC and transfers of beneficial interests will be facilitated only through records maintained by DTC and its participants.

The terms of the New Notes include those stated in the indenture and those made part of the indenture by reference to the Trust Indenture Act.

The following provides a summary of certain terms of the indenture and the New Notes. This summary is qualified in its entirety by reference to the complete indenture, which is incorporated by reference as an exhibit to the registration statement of which this prospectus is a part, and to the form of notes, which is included as an exhibit to the registration statement of which this prospectus is a part. We urge you to read the indenture and the form of notes because those documents, not this summary description, define your rights as holders of the New Notes. Whenever we refer to the defined terms of the indenture in this prospectus without defining them, the terms have the meanings given to them in the indenture. You must look to the indenture for the most complete description of the information summarized in this prospectus.

Unless otherwise indicated or the context otherwise requires, as used in this section, “we,” “our,” “us” and the “Company” refer only to Financial Institutions, Inc. and not to any of its subsidiaries.

General

The exchange offer for the New Notes will be for up to $80.0 million in aggregate principal amount of the Old Notes. The New Notes, together with any Old Notes that remain outstanding after the exchange offer, will be treated as a single class for all purposes of the indenture, including, without limitation, waivers, consents, amendments, prepayments and offers to purchase.

Principal, Maturity and Interest

The New Notes have materially identical interest terms as the Old Notes, except with respect to additional interest that may be earned on the Old Notes under circumstances relating to our registration obligations under the registration rights agreements. Interest on the notes will accrue from and including December 11, 2025. The notes will mature and become payable, unless earlier prepaid, on December 15, 2035.

From and including December 11, 2025 to but excluding December 15, 2030 or any earlier prepayment date, the New Notes will bear interest at a fixed annual rate equal to 6.50%, payable semi-annually in arrears on June 15 and December 15 of each year, beginning June 15, 2026. During this period, interest will be computed on the basis of a 360-day year consisting of twelve 30-day months. Interest on each New Note will accrue from the last interest payment date on which interest was paid on the Old Note surrendered in exchange thereof, or, if no interest has been paid on such Old Note, from the date of its original issuance. Interest on the Old Notes accepted for exchange will cease to accrue upon the issuance of the New Notes.

From and including December 15, 2030, to but excluding the maturity date or earlier prepayment date (the “Floating Rate Period”), the notes will bear interest at an annual floating rate, reset quarterly, equal to the Benchmark (which is expected to be Three-Month Term SOFR), plus a spread of 312 basis points; provided, however, that if the Three-Month Term SOFR (or other such Benchmark) is less than zero, Three-Month Term SOFR (or other such Benchmark) will be deemed to be zero. A “Floating Rate Interest Period” means the period from, and including, each Floating Interest Payment Date (as defined below) to, but excluding, the next succeeding Floating Interest Payment Date, except for the initial Floating Rate Interest Period, which will be the period from, and including, December 15, 2030 to, but excluding, the next succeeding Floating Interest Payment Date. During the Floating Rate Period, interest on the notes will be payable quarterly in arrears on March 15, June 15, September 15 and December 15 of each year (each a “Floating Interest Payment Date” and, together with any Fixed Interest Payment Date, an “Interest Payment Date”), and interest will be computed on the basis of a 360-day year and the actual number of days elapsed.

For the purpose of calculating the interest on the notes for each interest period during the Floating Rate Period when the Benchmark is Three-Month Term SOFR, “Three-Month Term SOFR” means the rate for Term SOFR for a tenor of three months that is published by the Term SOFR Administrator at the Reference Time for any Floating Rate Interest Period, as determined by the calculation agent after giving effect to the Three-Month Term SOFR Conventions. See “—Calculation Agent.” All percentages used in or resulting from any calculation of Three-Month Term SOFR will be rounded, if necessary, to the nearest one-hundred-thousandth of a percentage point, with 0.000005% rounded up to 0.00001%. We will act as the initial calculation agent.

The following definitions apply to the following discussion of Three-Month Term SOFR:

“Benchmark” means, initially, Three-Month Term SOFR; provided that if the calculation agent determines on or before the Reference Time for any Floating Rate Period that a Benchmark Transition Event and its related Benchmark Replacement Date have occurred with respect to Three-Month Term SOFR or the then-current Benchmark, then “Benchmark” means the applicable Benchmark Replacement for such Floating Rate Period and any subsequent Floating Rate Periods.

“Federal Reserve Bank of New York’s Website” means the website of the Federal Reserve Bank of New York at www.newyorkfed.org, or any successor source. The foregoing Internet website is an inactive textual reference only, meaning that the information contained on the website is not part of this prospectus supplement or the accompanying prospectus or incorporated by reference herein or therein.

“Interest period” means the period from and including the immediately preceding Interest Payment Date in respect of which interest has been paid or duly provided for or, if no interest has been paid or duly provided for, from and including the Issue Date to, but excluding, the applicable Interest Payment Date or the Maturity Date or date of earlier prepayment, if applicable.

“Reference Time” with respect to any determination of a Benchmark means: (i) if the Benchmark is Three-Month Term SOFR, the time determined by the calculation agent after giving effect to the Three-Month Term SOFR Conventions, and (ii) if the Benchmark is not Three-Month Term SOFR, the time determined by the calculation agent after giving effect to the Benchmark Replacement Conforming Changes.

“Relevant Governmental Body” means the Federal Reserve and/or the Federal Reserve Bank of New York, or a committee officially endorsed or convened by the Federal Reserve and/or the Federal Reserve Bank of New York, or any successor thereto.

“SOFR” means the secured overnight financing rate published by the Federal Reserve Bank of New York, as the administrator of the benchmark (or a successor administration), on the Federal Reserve Bank of New York’s website.

“Term SOFR” means the forward-looking term rate based on SOFR as published by the Term SOFR Administrator.

“Term SOFR Administrator” means CME Group Benchmark Administration Limited (CBA) (or a successor administrator of Three-Month Term SOFR selected by the calculation agent in its reasonable discretion).

“Three-Month Term SOFR Conventions” means any determination, decision or election with respect to any technical, administrative or operational matter (including with respect to the manner and timing of the publication of Three-Month Term SOFR, or changes to the definition of “interest period,” timing and frequency of determining Three-Month Term SOFR with respect to each interest period and making payments of interest, rounding of amounts or tenors, and other administrative matters) that the calculation agent decides may be appropriate to reflect the use of Three-Month Term SOFR as the Benchmark in a manner substantially consistent with market practice (or, if the calculation agent decides that adoption of any portion of such market practice is not administratively feasible or if the calculation agent determines that no market practice for the use of Three-Month Term SOFR exists, in such other manner as the calculation agent determines is reasonably necessary).

The terms “Benchmark Replacement,” “Benchmark Replacement Conforming Changes,” “Benchmark Replacement Date,” “Benchmark Transition Event” and “Corresponding Tenor” have the meanings set forth below under the heading “—Effect of Benchmark Transition Event.”

Notwithstanding the foregoing paragraphs related to the determination of interest, if the calculation agent determines on or before the relevant Reference Time that a Benchmark Transition Event and its related Benchmark Replacement Date (each as defined below) have occurred with respect to Three-Month Term SOFR, then the Company will promptly provide notice of such determination to the holders and the provisions set forth below under the heading “—Effect of Benchmark Transition Event,” which we refer to as the “benchmark transition provisions,” will thereafter apply to all determinations of the interest rate on the notes for each interest period during the Floating Rate Period. In accordance with the benchmark transition provisions, after a Benchmark Transition Event and its related Benchmark Replacement Date have occurred, the interest rate on the notes for each interest period during the Floating Rate Period will be an annual rate equal to the sum of the applicable Benchmark Replacement plus 312 basis points. Absent manifest error, the calculation agent’s determination of the interest rate for an interest period for the notes will be binding and conclusive on holders of the notes, the trustee and us.

Any payment of principal of or interest on the notes that would otherwise become due and payable on a day that is not a business day will become due and payable on the next succeeding business day, with the same force and effect as if made on the date for payment of such principal or interest (unless, with respect to a Floating Interest Payment Date, such day falls in the next calendar month, in which case the Floating Interest Payment Date will instead be the immediately preceding day that is a business day, and interest will accrue to the Floating Interest Payment Date as so adjusted), and no interest will accrue in respect of such payment for the period after such day.

If the then-current Benchmark is Three-Month Term SOFR, the calculation agent will have the right to establish the Three-Month Term SOFR Conventions, and if any of the foregoing provisions concerning the calculation of the interest rate and interest payments during the Floating Rate Period are inconsistent with any of

the Three-Month Term SOFR Conventions determined by the calculation agent, then the relevant Three-Month Term SOFR Conventions will apply. Furthermore, if the calculation agent determines that a Benchmark Transition Event and its related Benchmark Replacement Date have occurred with respect to Three-Month Term SOFR at any time when any of the New Notes are outstanding, the foregoing provisions concerning the calculation of the interest rate and interest payments during the Floating Rate Period will be modified in accordance with the benchmark transition provisions.

We will make each interest payment to the holders of record of the notes at the close of business on the fifteenth calendar day before the applicable Interest Payment Date. Principal of and interest on the notes will be payable, and the notes will be exchangeable and transferable, at the office or agency that we have designated and maintain for such purposes, which, initially, will be the offices of the trustee located at Wilmington Trust, National Association, 277 Park Ave, 25th Floor, New York, NY 10172; except that payment of interest may be made at our option by check mailed to the holder of record as shown on the security register or by wire transfer to an account appropriately designated by the person entitled to payment.

The term “business day” means any day other than a Saturday, Sunday or any other day on which banking institutions in the State of New York are authorized or obligated by law, regulation or executive order to close.

Effect of Benchmark Transition Event

Benchmark Replacement. If the calculation agent determines that a Benchmark Transition Event and its related Benchmark Replacement Date have occurred on or before the Reference Time in respect of any determination of the Benchmark on any date, then the Benchmark Replacement will replace the then-current Benchmark for all purposes relating to the notes during the Floating Rate Period in respect of such determination on such date and all determinations on all subsequent dates.

Benchmark Replacement Conforming Changes. In connection with the implementation of a Benchmark Replacement, the calculation agent will have the right to make Benchmark Replacement Conforming Changes from time to time.

Certain Defined Terms. As used herein:

“Benchmark Replacement” means the Interpolated Benchmark with respect to the then-current Benchmark, plus the Benchmark Replacement Adjustment for such Benchmark; provided that if: (a) the calculation agent cannot determine the Interpolated Benchmark as of the Benchmark Replacement Date, or (b) the then-current Benchmark is Three-Month Term SOFR and a Benchmark Transition Event and its related Benchmark Replacement Date have occurred with respect to Three-Month Term SOFR (in which event no Interpolated Benchmark with respect to Three-Month Term SOFR will be determined), then “Benchmark Replacement” means the first alternative set forth in the order below that can be determined by the calculation agent as of the Benchmark Replacement Date:

(1) the sum of (i) Compounded SOFR and the (ii) Benchmark Replacement Adjustment;

(2) the sum of: (i) the alternate rate that has been selected or recommended by the Relevant Governmental Body as the replacement for the then-current Benchmark for the applicable Corresponding Tenor and (ii) the Benchmark Replacement Adjustment;

(3) the sum of: (i) the ISDA Fallback Rate and (ii) the Benchmark Replacement Adjustment; or

(4) the sum of: (i) the alternate rate that has been selected by the calculation agent as the replacement for the then-current Benchmark for the applicable Corresponding Tenor giving due consideration to any industry-accepted rate as a replacement for the then-current Benchmark for U.S. dollar-denominated floating rate securities at such time, and (ii) the Benchmark Replacement Adjustment.

If the Benchmark Replacement as determined pursuant to clause (a), (b), (c) or (d) above would be less than zero, the Benchmark Replacement will be deemed to be zero.

“Benchmark Replacement Adjustment” means the first alternative set forth in the order below that can be determined by the calculation agent as of the Benchmark Replacement Date:

(1) the spread adjustment, or method for calculating or determining such spread adjustment (which may be a positive or negative value or zero), that has been selected or recommended by the Relevant Governmental Body for the applicable Unadjusted Benchmark Replacement;

(2) if the applicable Unadjusted Benchmark Replacement is equivalent to the ISDA Fallback Rate, then the ISDA Fallback Adjustment; or

(3) the spread adjustment (which may be a positive or negative value or zero) that has been selected by the calculation agent giving due consideration to any industry-accepted spread adjustment or method for calculating or determining such spread adjustment, for the replacement of the then-current Benchmark with the applicable Unadjusted Benchmark Replacement for U.S. dollar-denominated floating rate securities at such time.

“Benchmark Replacement Conforming Changes” means, with respect to any Benchmark Replacement, any technical, administrative or operational changes (including, without limitation, changes to the definition of “interest period,” timing and frequency of determining rates with respect to each interest period and making payments of interest, rounding of amounts or tenors, and other administrative matters) that the calculation agent or the Company decides may be appropriate to reflect the adoption of such Benchmark Replacement in a manner substantially consistent with market practice (or, if the calculation agent or the Company decides that adoption of any portion of such market practice is not administratively feasible or if the calculation agent determines that no market practice for use of the Benchmark Replacement exists, in such other manner as the calculation agent determines is reasonably necessary).

“Benchmark Replacement Date” means the earliest to occur of the following events with respect to the then-current Benchmark:

(1) in the case of clause (1) of the definition of “Benchmark Transition Event,” the relevant Reference Time in respect of any determination;

(2) in the case of clause (2) or (3) of the definition of “Benchmark Transition Event,” the later of (i) the date of the public statement or publication of information referenced therein and (ii) the date on which the administrator of the Benchmark permanently or indefinitely ceases to provide the Benchmark; or

(3) in the case of clause (4) of the definition of “Benchmark Transition Event,” the date of the public statement or publication of information referenced therein.

For the avoidance of doubt, for purposes of the definitions of Benchmark Replacement Date and Benchmark Transition Event, references to the Benchmark also include any reference rate underlying the Benchmark (for example, if the Benchmark becomes compounded SOFR, references to the Benchmark would include SOFR).

For the avoidance of doubt, if the event giving rise to the Benchmark Replacement Date occurs on the same day as, but earlier than, the Reference Time in respect of any determination, the Benchmark Replacement Date will be deemed to have occurred before the Reference Time for purposes of such determination.

“Benchmark Transition Event” means the occurrence of one or more of the following events with respect to the then-current Benchmark:

(1) if the Benchmark is Three-Month Term SOFR, the calculation agent or the Company determines that the use of a forward-looking rate for a tenor of three months based on SOFR is not administratively feasible;

(2) a public statement or publication of information by or on behalf of the administrator of the Benchmark announcing that such administrator has ceased or will cease to provide the Benchmark, permanently or indefinitely, provided that, at the time of such statement or publication, there is no successor administrator that will continue to provide the Benchmark;

(3) a public statement or publication of information by the regulatory supervisor for the administrator of the Benchmark, the central bank for the currency of the Benchmark, an insolvency official with jurisdiction over the administrator for the Benchmark, a resolution authority with jurisdiction over the administrator for the Benchmark or a court or an entity with similar insolvency or resolution authority over the administrator for the Benchmark, which states that the administrator of the Benchmark has ceased or will cease to provide the Benchmark permanently or indefinitely, provided that, at the time of such statement or publication, there is no successor administrator that will continue to provide the Benchmark; or

(4) a public statement or publication of information by the regulatory supervisor for the administrator of the Benchmark announcing that the Benchmark is no longer representative.

“Compounded SOFR” means the compounded average of SOFRs for the applicable Corresponding Tenor, with the rate, or methodology for this rate, and conventions for this rate being established by the calculation agent in accordance with:

(1) the rate, or methodology for this rate, and conventions for this rate selected or recommended by the Relevant Governmental Body for determining Compounded SOFR; provided that:

(2) if, and to the extent that, the calculation agent determines that Compounded SOFR cannot be determined in accordance with clause (1) above, then the rate, or methodology for this rate, and conventions for this rate that have been selected by the calculation agent giving due consideration to any industry-accepted market practice for U.S. dollar-denominated floating rate securities at such time.

For the avoidance of doubt, the calculation of Compounded SOFR will exclude the Benchmark Replacement Adjustment (if applicable) and the spread of 312 basis points.

“Corresponding Tenor” means (i) with respect to Three-Month Term SOFR, three months, and (ii) with respect to a Benchmark Replacement, a tenor (including overnight) having approximately the same length (disregarding Business Day adjustment) as the applicable tenor for the then-current Benchmark.

“Interpolated Benchmark” with respect to the Benchmark means the rate determined by the calculation agent for the Corresponding Tenor by interpolating on a linear basis between: (1) the Benchmark for the longest period (for which the Benchmark is available) that is shorter than the Corresponding Tenor, and (2) the Benchmark for the shortest period (for which the Benchmark is available) that is longer than the Corresponding Tenor.

“ISDA” means the International Swaps and Derivatives Association, Inc. or any successor thereto.

“ISDA Definitions” means the 2021 ISDA Interest Rate Definitions published by ISDA, as amended or supplemented from time to time, or any successor definitional booklet for interest rate derivatives published from time to time.

“ISDA Fallback Adjustment” means the spread adjustment (which may be a positive or negative value or zero) that would apply for derivatives transactions referencing the ISDA Definitions to be determined upon the occurrence of an index cessation event with respect to the Benchmark for the applicable tenor.

“ISDA Fallback Rate” means the rate that would apply for derivatives transactions referencing the ISDA Definitions to be effective upon the occurrence of an index cessation date with respect to the Benchmark for the applicable tenor excluding the applicable ISDA Fallback Adjustment.

“Unadjusted Benchmark Replacement” means the Benchmark Replacement excluding the Benchmark Replacement Adjustment.

The terms “FRBNY’s Website,” “Reference Time,” “Relevant Governmental Body,” “SOFR” and “Term SOFR” have the meanings set forth above under the heading “Principal, Maturity and Interest.”

Subordination

As of September 30, 2025, we had consolidated total assets of $6.29 billion, total loans of $4.59 billion, total deposits of $5.36 billion and total shareholders’ equity of $621.7 million.

Our obligation to make any payment on account of the principal of, or interest on, the notes will be subordinate and junior in right of payment to the prior payment in full of all senior indebtedness. As of September 30, 2025, the Company’s subsidiaries had, in the aggregate, outstanding debt and deposits of $5.67 billion. In addition, as of September 30, 2025, the Company had no indebtedness that would rank senior to the New Notes, no indebtedness that would rank pari passu with the New Notes (other than the Old Notes), and no indebtedness that would rank subordinate to the New Notes. The notes do not limit the amount of additional indebtedness, including senior indebtedness that we or any of our subsidiaries, including the Bank, may incur in the future.

The term “Senior Indebtedness” means (1) all indebtedness and obligations of, or guaranteed or assumed by, the Company for money borrowed, whether or not evidenced by bonds, debentures, securities, notes or other similar instruments, and including, but not limited to all obligations to the Company’s general and secured creditors; (2) any deferred obligations of the Company for the payment of the purchase price of property or assets acquired other than in the ordinary course of business; (3) all obligations, contingent or otherwise, of the Company in respect of any letters of credit, bankers’ acceptances, security purchase facilities and similar direct credit substitutes; (4) any capital lease obligations of the Company; (5) all obligations of the Company in respect of interest rate swap, cap or other agreements, interest rate future or option contracts, currency swap agreements, currency future or option contracts, commodity contracts and other similar arrangements or derivative products; (6) all obligations that are similar to those in clauses (1) through (5) of other persons for the payment of which the Company is responsible or liable as obligor, guarantor or otherwise arising from an off-balance sheet guarantee; (7) all obligations of the types referred to in clauses (1) through (6) of other persons secured by a lien on any property or asset of the Company; and (8) in the case of (1) through (7) above, all amendments, renewals, extensions, modifications and refundings of such indebtedness and obligations. Notwithstanding the foregoing, “Senior Indebtedness” does not include (a) the notes, (b) any obligation that by its terms expressly is junior to, or ranks equally in right of payment with, the Subordinated Notes, or (c) any indebtedness between the Company and any of its subsidiaries or Affiliates.

In accordance with the subordination provisions of the indenture and the notes, we are permitted to make payments of accrued and unpaid interest on the notes on the interest payment dates and at maturity and to pay the principal of the notes at maturity unless:

•

we are subject to any termination, winding up, liquidation or reorganization, whether in bankruptcy, insolvency, reorganization or receivership proceedings or upon an assignment for the benefit of our creditors or any other marshalling of our assets and liabilities; or

•

a default in the payment of principal of, or premium, if any, or interest on, any senior indebtedness, has occurred and is continuing beyond any applicable grace period, or an event of default has occurred and is continuing with respect to any senior indebtedness, or would occur as a result of a payment of principal of, or interest on, the notes being made and that event of default would permit the holders of any senior indebtedness (or a trustee on behalf of the holders thereof) to accelerate the maturity of that senior indebtedness and such default or event of default has not been cured, waived or otherwise have ceased to exist.

Upon our termination, winding up, liquidation or reorganization, whether in bankruptcy, insolvency, reorganization or receivership proceedings or upon an assignment for the benefit of our creditors or any other marshalling of our assets and liabilities or otherwise, we must pay to the holders of all of our senior indebtedness the full amounts of principal of, premium, if any, and interest due on, that senior indebtedness before any payment is made on the notes. If, after we have paid the senior indebtedness in full, there are any amounts available for payment of the notes and any of our other indebtedness and obligations ranking equally in right of payment with the notes, then we will use such remaining assets to pay the amounts of principal of, premium, if any, and accrued and unpaid interest on, the notes and such other of our indebtedness and obligations that rank equally in right of payment with the notes. If those assets are insufficient to pay in full the principal of, premium, if any, and interest on the notes and such other indebtedness and obligations, those assets will be applicable ratably to the payment of such amounts owing with respect to the notes and such other indebtedness and obligations.

If we are subject to any termination, winding up, liquidation or reorganization, whether in bankruptcy, insolvency, reorganization or receivership proceedings or upon an assignment for the benefit of our creditors or any other marshalling of our assets and liabilities or otherwise, if the holders of the notes receive for any reason any payment on the notes or other distributions of our assets with respect to the notes before all of our senior indebtedness is paid in full, the holders of the notes will be required to return that payment or distribution to the trustee in bankruptcy, receiver, liquidating trustee, custodian, assignee, agent or other person making payment of our assets for all our senior indebtedness remaining unpaid until all such senior indebtedness has been paid in full, after giving effect to any concurrent payment or distribution to the holders of such senior indebtedness.

As a result of the subordination of the notes in favor of the holders of our senior indebtedness, in the event of our bankruptcy or insolvency, holders of our senior indebtedness may receive more, ratably, and holders of the notes may receive less, ratably, than our other creditors.

All liabilities of the Bank and our other subsidiaries, including deposits and liabilities to general creditors arising during the ordinary course of business or otherwise, will be effectively senior in right of payment to the notes to the extent of the assets of the subsidiary because, as a shareholder of the subsidiary, we do not have any rights to the assets of the subsidiary except if the subsidiary declares a dividend payable to us or if there are assets of the subsidiary remaining after it has discharged its liabilities to its creditors in connection with its liquidation. Over the term of the notes, we will need to rely primarily on dividends paid to us by the Bank, which is a regulated and supervised depository institution, for the funds necessary to pay the interest on our outstanding debt obligations and to make dividends and other payments on our other securities outstanding now or in the future. With respect to the payment of the principal of the notes at their maturity, we may rely on the funds we receive from dividends paid to us by the Bank, but may have to rely on the proceeds of borrowings and/or the sale of other securities to pay the principal amount of the notes. Regulatory rules may restrict the Bank’s ability to pay dividends or make other distributions to us or provide funds to us by other means. As a result, with respect to the assets of the Bank, our creditors (including the holders of the notes) are structurally subordinated to the prior claims of creditors of the Bank, including its depositors, except to the extent that we may be a creditor with recognized claims against the Bank.

Prepayment

We may, at our option, subject to regulatory approval, prepay the notes, in whole or in part, on or after December 15, 2030. In addition, at our option, subject to regulatory approval, we may prepay the notes, in whole or in part, at any time upon the occurrence of:

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a “Tier 2 Capital Event,” which means our good faith determination that, as a result of (a) any amendment to, or change in, the laws, rules or regulations of the United States (including, for the avoidance of doubt, any agency or instrumentality of the United States, including the Federal Reserve or other federal bank regulatory agencies) or any political subdivision of or in the United States that is

enacted or becomes effective after December 11, 2025; (b) any proposed change in those laws, rules or regulations that is announced or becomes effective after December 11, 2025; or (c) any official administrative decisions or judicial decisions or administrative action or other official pronouncement interpreting or applying those laws, rules, regulations, policies or guidelines with respect thereto that is announced after December 11, 2025, there is more than an insubstantial risk that we will not be entitled to treat the notes then outstanding as “Tier 2 Capital” (or its equivalent) for purposes of the capital adequacy rules or regulations of the Board of Governors of the Federal Reserve System (or its designee) or any successor agency, and any other bank regulatory agency (or, as and if applicable, the capital adequacy rules of regulations of any successor appropriate federal banking agency) as then in effect and applicable to us, for so long as any notes are outstanding;

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a “Tax Event,” which means the receipt by the Company of a legal opinion from counsel experienced in such matters to the effect that, as a result of any amendment to, or change (including any final and adopted (or enacted) prospective change) in, the laws (or any regulations thereunder) of the United States or any political subdivision or taxing authority thereof or therein, or as a result of any change in official administrative pronouncement or judicial decision interpreting or applying such laws or regulations, there is more than an insubstantial risk that interest payable by the Company on the notes is not, or within 90 days of the date of such opinion will not be, deductible by the Company, in whole or in part, for United States federal income tax purposes; or

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an “Investment Company Event,” which means the receipt by the Company of a legal opinion from counsel experienced in such matters to the effect that there is more than an insubstantial risk that the Company is or, within 90 days after the receipt of such opinion will be, required to register as an investment company pursuant to the Investment Company Act of 1940, as amended.

Any prepayment of the notes will be at a prepayment price equal to 100% of the principal amount of the notes being prepaid, plus accrued and unpaid interest, if any, and additional interest, if and to the extent applicable, thereon to but excluding the date of prepayment. Any prepayment of the notes will be subject to any required regulatory approvals, including the Federal Reserve (or its designee) or any successor agency, and any other bank regulatory agency, to the extent such approval shall then be required by law, regulation or policy.

If less than all of the notes are to be prepaid, the notes will be prepaid on a pro rata basis as to the holders, and such prepayment will be made on a “Pro Rata Pass-Through Distribution of Principal” basis in accordance with the procedures of DTC.

Notices of prepayment will be given in the manner provided for in the indenture to each holder of notes to be prepaid not less than 10 nor more than 45 days before the prepayment date. If any note is to be prepaid in part only, the notice of prepayment that relates to that note will state the portion of the principal amount thereof to be prepaid. Notes, or a portion of the notes, called for prepayment become due and payable on the date fixed for prepayment at the prepayment price specified in the notice of prepayment, together with any accrued and unpaid interest, if any, and additional interest, if and to the extent applicable. On and after the prepayment date, interest ceases to accrue on notes or portions of notes called for prepayment.

The notes are not subject to prepayment at the option of the holders.

Repurchases

We may purchase notes at any time on the open market or otherwise. If we purchase notes in this manner, we have the discretion to hold, resell or surrender the notes to the trustee under the indenture for cancellation.

No Sinking Fund; Non-Convertible

The notes will not be entitled to the benefit of any sinking fund. Except as contemplated by this prospectus, the notes are not convertible into, or exchangeable for, any of our or our subsidiaries’ equity securities, other securities or assets.

Form, Denomination, Transfer, Exchange and Book-Entry Procedures

The notes will be issued only in registered form without coupons and in minimum denominations of $100,000 and any integral multiple of $1,000 in excess thereof.

The New Notes will be evidenced by one or more global notes that will be deposited with, or on behalf of, DTC, or any successor thereto, and registered in the name of Cede & Co. as nominee of DTC. Except as set forth below, record ownership of the global notes may be transferred, in whole or in part, only to another nominee of DTC or to a successor of DTC or its nominee.

The global notes will not be registered in the name of any person, or exchanged for notes that are registered in the name of any person, other than DTC or its nominee, unless one of the following occurs:

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DTC notifies us that it is unwilling or unable to continue acting as the depositary for the global notes, or DTC has ceased to be a clearing agency registered under the Exchange Act, and in either case we do not appoint a successor depositary within 90 days;

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we determine that the notes are no longer to be represented by the global notes and so notify the trustee in writing; or

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an event of default with respect to the notes has occurred and is continuing and DTC has requested the issuance of definitive subordinated notes.

In those circumstances, DTC will determine in whose names any securities issued in exchange for the global notes will be registered. Any such notes in certificated form will be issued in minimum denominations of $100,000 and any integral multiples of $1,000 in excess thereof and may be transferred or exchanged only in such minimum denominations.

DTC or its nominee will be considered the sole owner and holder of the global notes for all purposes, and as a result:

•

you cannot receive notes registered in your name if they are represented by the global notes;

•

you cannot receive certificated (physical) notes in exchange for your beneficial interest in the global notes;

•

you will not be considered to be the owner or holder of the global notes or any note it represents for any purpose; and

•

all payments on the global notes will be made to DTC or its nominee.

The laws of some jurisdictions require that certain kinds of purchasers (for example, certain insurance companies) can only own securities in certificated form. These laws may limit your ability to transfer your beneficial interests in the global notes to these types of purchasers.

Only institutions (such as a securities broker or dealer) that have accounts with DTC or its nominee, referred to as “participants,” and persons that may hold beneficial interests through participants (including through Euroclear Bank SA/NV or Clearstream Banking, societe anonyme, as DTC participants) can own a beneficial interest in the global notes. The only place where the ownership of beneficial interests in the global notes will appear and the only way the transfer of those interests can be made will be on the records kept by DTC (for their participants’ interests) and the records kept by those participants (for interests of persons held by participants on their behalf).

Secondary trading in bonds and notes of corporate issuers is generally settled in clearinghouse (that is, next day) funds. In contrast, beneficial interests in global notes usually trade in DTC’s same-day funds settlement system and settle in immediately available funds. We make no representations as to the effect that settlement in immediately available funds will have on trading activity in those beneficial interests.

Cash payments of interest on and principal of the global notes will be made to Cede & Co., the nominee for DTC, as the registered owner of the global notes. These payments will be made by wire transfer of immediately available funds on each payment date.

You may exchange or transfer the notes at the corporate trust office of the trustee for the notes or at any other office or agency maintained by us for those purposes. We will not require payment of a service charge for any transfer or exchange of the notes, but we may require payment of a sum sufficient to cover any applicable tax or other governmental charge.

We have been informed that, with respect to any cash payment of interest on or principal of the global notes, DTC’s practice is to credit participants’ accounts on the payment date with payments in amounts proportionate to their respective beneficial interests in the notes represented by the global notes as shown on DTC’s records, unless DTC has reason to believe that it will not receive payment on that payment date. Payments by participants to owners of beneficial interests in notes represented by the global notes held through participants will be the responsibility of those participants, as is now the case with securities held for the accounts of customers registered in “street name.”

We also understand that neither DTC nor Cede & Co. will consent or vote with respect to the notes. We have been advised that, under its usual procedures, DTC will mail an “omnibus proxy” to us as soon as possible after the record date. The omnibus proxy assigns Cede & Co.’s consenting or voting rights to those participants to whose accounts the notes are credited on the record date identified in a listing attached to the omnibus proxy.

Because DTC can only act on behalf of participants, who in turn act on behalf of indirect participants, the ability of a person having a beneficial interest in the principal amount represented by the global notes to pledge the interest to persons or entities that do not participate in the DTC book-entry system, or otherwise take actions in respect of that interest, may be affected by the lack of a physical certificate evidencing its interest.

DTC has advised that it will take any action permitted to be taken by a holder of notes (including the presentation of notes for exchange) only at the direction of one or more participants to whose account with DTC interests in the global notes are credited and only in respect of such portion of the principal amount of the notes represented by the global notes as to which such participant has, or participants have, given such direction.

DTC has also advised as follows: DTC is a limited purpose trust company organized under the laws of the State of New York, a “banking organization” within the meaning of the New York Banking Law, a member of the Federal Reserve, a “clearing corporation” within the meaning of the Uniform Commercial Code, as amended, and a “clearing agency” registered pursuant to the provisions of Section 17A of the Exchange Act. DTC was created to hold securities for its participants and facilitate the clearance and settlement of securities transactions between participants through electronic book-entry changes in accounts of its participants. Participants include securities brokers and dealers, banks, trust companies and clearing corporations and may include certain other organizations. Certain of such participants (or their representatives), together with other entities, own DTC. Indirect access to the DTC system is available to other entities such as banks, brokers, dealers and trust companies that clear through or maintain a custodial relationship with a participant, either directly or indirectly. The rules applicable to DTC and its direct and indirect participants are on file with the SEC.

The policies and procedures of DTC, which may change periodically, will apply to payments, transfers, exchanges and other matters relating to beneficial interests in the global notes. We and the trustee have no responsibility or liability for any aspect of DTC’s or any participants’ records relating to beneficial interests in the global notes, including for payments made on the global notes, and we and the trustee are not responsible for maintaining, supervising or reviewing any of those records.

Indenture Covenants

The indenture contains no covenants or restrictions on the incurrence of indebtedness or other obligations by us or by a subsidiary of ours, including the Bank. The indenture contains no financial covenants requiring us to achieve or maintain any minimum financial results relating to our financial condition, liquidity or results of operations or meet or exceed any financial ratios, to incur additional indebtedness or obligations or to maintain any reserves. Moreover, neither the indenture nor the notes contain any covenants prohibiting us or our subsidiaries from or limiting our or our subsidiaries’ right to incur additional indebtedness or obligations, grant liens on our assets to secure our indebtedness or other obligations that are senior in right of payment to the notes, repurchase our stock or other securities, including any of the notes, or pay dividends or make other distributions to our shareholders (except, subject to certain limited exceptions, in the case of dividends or other distributions, redemptions, purchases, acquisitions or liquidation payments with respect to our capital stock and repayments, repurchases or redemptions of any debt securities that rank equal with or junior to the notes, in each case, upon our failure to make any required payment of principal or interest on the notes, when the same becomes due and payable). In addition, neither the indenture nor the notes contain any provision that would provide protection to the holders of the notes against a material decline in our credit quality.

Events of Default; Right of Acceleration; Failure to Pay Principal or Interest

The following are events of default under the indenture:

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the entry of a court decree or order for relief in respect of us by a court having jurisdiction in the premises in an involuntary case or proceeding under any applicable bankruptcy, insolvency, or reorganization law, now or hereafter in effect of the United States or any political subdivision thereof, and such decree or order will have continued unstayed and in effect for a period of 60 consecutive days;

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the commencement by us of a voluntary case under any applicable bankruptcy, insolvency or reorganization law, now or hereafter in effect of the United States or any political subdivision thereof, or the consent by us to the entry of a decree or order for relief in an involuntary case or proceeding under any such law;

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the appointment by a competent government agency having primary regulatory authority over any Major Constituent Bank subsidiary of ours, as defined in the Indenture, under any applicable federal or state banking, insolvency or similar law now or hereafter in effect of a receiver of any such Major Constituent Bank, or the entry of a decree or order in any case or proceeding under any applicable federal or state banking, insolvency or other similar law now or hereafter in effect appointing any receiver of any Major Constituent Bank;

•

our failure to make payment of any installment of interest on the notes as and when due and payable, which continues for a period of 30 days;

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our failure to make payment of all or any part of the principal of the notes as and when due and payable under the indenture;

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our failure to perform any other of our or its obligations under the notes or the indenture, which continues for a period of 60 days after written notice is given as provided for in the indenture; and

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the default by us, under any of our other indebtedness having an aggregate principal amount of at least $25,000,000, whether such indebtedness now exists or is created or incurred in the future, which default (1) constitutes failure in payment of principal of such indebtedness when due after the expiration of any applicable grace period without such indebtedness having been discharged or (2) results in such indebtedness becoming due or being declared due and payable before the date on which it otherwise would have become due or payable without, in the case of clause (1), such indebtedness having been discharged or, in the case of clause (2), without such indebtedness having been discharged or such acceleration having been rescinded or annulled.

If an event of default with respect to the notes occurs due to a bankruptcy event described in the first two bullets above, the outstanding principal amount of the notes and all accrued and unpaid interest, if any, thereon will be immediately due and payable without any declaration or other act on the part of the trustee or any holder of the notes. If an event of default with respect to the notes occurs due to any reason other than a bankruptcy event described in the first two bullets above, neither the trustee nor any holder may accelerate the maturity of the notes and make the principal of, and any accrued and unpaid interest on, the notes immediately due and payable.

Under the indenture, if we fail to make any payment of interest on any note when such interest becomes due and payable and such default continues for a period of 30 days, or if we fail to make any payment of the principal of any note when such principal becomes due and payable, the trustee may, subject to certain limitations and conditions, demand, for the benefit of the holders of the notes, that we pay to the trustee, for the benefit of the holders of the notes, the whole amount then due and payable with respect to the notes, with interest upon the overdue principal, and, to the extent permitted by applicable law, upon any overdue installments of interest at the rate or respective rates, as the case may be, provided for or with respect to the notes or, if no such rate or rates are so provided, at the rate or respective rates, as the case may be, of interest borne by the notes.

Any rights to receive payment of such amounts under the notes remain subject to the subordination provisions of the notes as discussed above under “—Subordination.” Neither the trustee nor the holders of the notes will have the right to accelerate the maturity of the notes in the case of our failure to pay the principal of, or interest on, the notes or our non-performance of any other covenant or warranty under the notes or the indenture.

Amendment, Supplement and Waiver

Without the consent of any holder of notes, we and the trustee, at any time and from time to time, may enter into one or more indentures supplemental to the indenture for any of the following purposes:

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to evidence a successor to our organization, and the assumption by any such successor of our covenants contained in the indenture and the notes;

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to add to our covenants for the benefit of the holders, or to surrender any right or power conferred upon us with respect to the notes;

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to permit or facilitate the issuance of notes in uncertificated or global form, as long as any such action will not adversely affect the interests of the holders;

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to evidence and provide for the acceptance of appointment under the indenture by a successor trustee and to add to or change any provisions of the indenture to provide for or facilitate the administration of the trusts under the indenture by more than one trustee;

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to cure any ambiguity or to correct or supplement any provision in the indenture that may be defective or that may be inconsistent with any other provision thereof;

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to make any other provisions with respect to matters or questions arising under the indenture that will not adversely affect the interests of the holders of the notes;

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to include additional events of default;

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to supplement any of the provisions of the indenture to the extent necessary to permit or facilitate legal or covenant defeasance, or satisfaction and discharge of the notes, as long as any such action will not adversely affect the interests of any holder;

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to provide for the issuance of the New Notes in connection with the exchange offer;

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to conform any provision of the indenture to the requirements of the Trust Indenture Act; or

•

to make any change that does not adversely affect the legal rights under the indenture of any holder.

With the consent of the holders of not less than a majority of the then-outstanding aggregate principal amount of the notes, we and the trustee may enter into an indenture or indentures supplemental to the indenture to add any provisions to or change in any manner or eliminate any of the provisions of the indenture or the notes or of modify in any manner the rights of the holders of the notes under the indenture, except that no such supplemental indenture, without the consent of the holder of each outstanding note affected thereby, will:

•

reduce the rate of, or change the time for payment of, interest on any note;

•

reduce the principal of or change the stated maturity of any note, change the date on which any note may be subject to prepayment, or reduce the price at which any note subject to prepayment may be prepaid;

•

make any note payable in money other than U.S. dollars;

•

make any change in provisions of the indenture protecting the right of a holder to receive payment of principal of and interest on such note on or after the due date thereof or to bring suit to enforce payment;

•

reduce the threshold of holders the consent of whom is required for any such supplemental indenture or required to waive certain defaults and covenants under the indenture; or

•

modify any of the provisions of the section of the indenture governing supplemental indentures with the consent of holders, or those provisions relating to waiver of defaults or certain covenants, except to increase any such percentage required for such actions or to provide that certain other provisions of the indenture cannot be modified or waived without the consent of the holder of each outstanding note affected thereby.

The holders of not less than a majority the then-outstanding aggregate principal amount of the notes may on behalf of the holders of all notes waive any past default under the indenture and its consequences, except a default in any payment in respect of the principal of or interest on any note, or in respect of a covenant or provision of the indenture under which the indenture cannot be modified or amended without the consent of the holder of each outstanding note.

Satisfaction and Discharge of the Indenture; Defeasance

We may terminate our obligations under the indenture when:

•

either: (a) all notes that have been authenticated and delivered have been delivered to the trustee for cancellation, or (b) all notes that have not been delivered to the trustee for cancellation (1) have become due and payable or (2) will become due and payable at their stated maturity within one year or (3) if subject to repurchase or prepayment at the option of the Company, are to be called for repurchase or prepaid in full within one year under arrangements satisfactory to the trustee for the giving of notice of prepayment by the trustee, and in the case of the foregoing clause (b)(1), (b)(2) or (b)(3), we have deposited or caused to be deposited with the trustee immediately available funds in an amount sufficient to pay and discharge the entire indebtedness on the outstanding notes;

•

we have paid or caused to be paid all other sums payable by us under the indenture with respect to the notes; and

•

we have delivered to the trustee an officer’s certificate and an opinion of counsel, each stating that all conditions precedent under the indenture relating to the satisfaction and discharge of the indenture have been satisfied.

We may elect, at our option and at any time, to have our obligations discharged with respect to the outstanding notes, which we refer to as legal defeasance. Legal defeasance means that we will be deemed to have paid and discharged the entire indebtedness represented by the outstanding notes, except for:

•

the rights of the holders of such notes to receive, solely from the trust fund established in accordance with the indenture and described below, payments in respect of the principal of and interest, if any, on such notes when payments are due;

•

our obligations and the obligations of the trustee with respect to such notes under the indenture concerning registration of notes, mutilated, destroyed, lost or stolen notes, the maintenance of an office or agency for payment and money for payments on the notes to be held in trust;

•

the rights, powers, trusts, duties and immunities of the trustee under the indenture; and

•

the defeasance provisions and the application of trust money provisions of the indenture.

In addition, we may elect, at our option, to have our obligations released with respect to certain covenants contained in the indenture, which is also called covenant defeasance. If a covenant defeasance occurs, certain events (not including non-payment, bankruptcy and insolvency events) will no longer constitute an event of default with respect to the notes.

To exercise either legal defeasance or covenant defeasance with respect to outstanding notes:

•

we must irrevocably have deposited or caused to be deposited with the trustee as trust funds in trust for the purpose of making the following payments, specifically pledged as security for, and dedicated solely to the benefits of the holders of such notes, (1) U.S. dollars, (2) U.S. government obligations that through the scheduled payment of principal and interest in respect thereof in accordance with their terms will provide, not later than one day before the due date of any payment on the notes, money, or (3) a combination thereof, in each case in an amount sufficient to pay and discharge, and which will be applied by the trustee to pay and discharge, the entire indebtedness in respect of the principal of and interest on the notes on the stated maturity thereof or, with respect to notes called for prepayment, on the prepayment date thereof;

•

such legal defeasance or covenant defeasance will not result in a breach or violation of, or constitute a default under, the indenture or any other material agreement or material instrument to which we or our subsidiaries are a party or by which we or our subsidiaries are bound;

•

no event of default, or event which with notice or lapse of time or both would become an event of default with respect to the outstanding notes, will have occurred and be continuing on the date of such deposit referred to in the first bullet point above (and in the case of legal defeasance, will have occurred and be continuing at any time during the period ending on and including the 91^st day after the date of such deposit);

•

in the case of legal defeasance, we will have delivered to the trustee an opinion of counsel stating that we have received from, or there has been published by, the Internal Revenue Service a ruling, or since the date of the indenture there has been a change in applicable U.S. federal income tax law, in either case to the effect that, and based thereon such opinion will confirm that, the holders of the notes will not recognize income, gain or loss for U.S. federal income tax purposes as a result of such legal defeasance to be effected with respect to such notes and will be subject to U.S. federal income tax on the same amounts, in the same manner and at the same times as would be the case if such legal defeasance had not occurred;

•

in the case of covenant defeasance, we will have delivered to the trustee an opinion of counsel to the effect that the holders of the outstanding notes will not recognize income, gain or loss for U.S. federal income tax purposes as a result of such covenant defeasance to be effected with respect to the notes and will be subject to U.S. federal income tax on the same amounts, in the same manner and at the same times as would be the case if such covenant defeasance had not occurred;

•

we will have delivered to the trustee an officer’s certificate and an opinion of counsel, each stating that all conditions precedent with respect to such legal defeasance or covenant defeasance have been satisfied;

•

we will have given the trustee irrevocable instructions to prepay the notes and provide notice of prepayment to holders; and

•

the trustee will have received such other documents, assurances, and opinions of counsel as reasonably required.

In connection with a discharge or defeasance, if the trustee is unable to apply the moneys deposited as contemplated under the satisfaction and discharge provisions of the indenture for any reason, our obligations under the indenture and the notes will be revived as if the deposit had never occurred.

Calculation Agent

We will appoint a calculation agent for the notes before the commencement of the Floating Rate Period. We or an affiliate of ours may assume the duties of the calculation agent. We will act as the initial calculation agent.

Determinations and Decisions

The calculation agent is expressly authorized to make certain determinations, decisions and elections under the terms of the notes, including with respect to the use of Three-Month Term SOFR as the Benchmark for the Floating Rate Period and under the benchmark transition provisions. Any determination, decision or election that may be made by the calculation agent under the terms of the notes, including any determination with respect to a tenor, rate or adjustment or of the occurrence or non-occurrence of an event, circumstance or date and any decision to take or refrain from taking any action or any selection:

•

will be conclusive and binding on the holders of the notes and the trustee absent manifest error;

•

if made by us as calculation agent, will be made in our sole discretion;

•

if made by a calculation agent other than us, will be made after consultation with us, and the calculation agent will not make any such determination, decision or election to which we reasonably object; and

•

notwithstanding anything to the contrary in the indenture, will become effective without consent from the holders of the notes, the trustee or any other party.

Regarding the Trustee

Wilmington Trust, National Association is acting as the trustee under the indenture and the initial paying agent and registrar for the notes. From time to time, we and some of our subsidiaries may maintain deposit accounts and conduct other banking transactions, including lending transactions, with the trustee in the ordinary course of business.

Except during the continuance of an event of default under the indenture, the trustee will perform only such duties as are specifically set forth in the indenture.

The indenture and the Trust Indenture Act contain certain limitations on the rights of the trustee, if it becomes a creditor of our organization, to obtain payment of claims in certain cases or to realize on certain property received in respect of any such claim as security or otherwise. The trustee will be permitted to engage in other transactions; however, if it acquires any “conflicting interest” (as defined in the Trust Indenture Act), it must eliminate such conflict within 90 days and apply to the SEC for permission to continue or resign.

The holders of a majority in aggregate principal amount of the outstanding notes will have the right to direct the time, place and method of conducting any proceeding for any remedy available to the trustee or to exercise any trust or power conferred on the trustee, subject to certain exceptions. If an event of default has occurred and is continuing, the trustee will exercise such of the rights and powers vested in it by the indenture and use the same degree of care and skill in its exercise, as a prudent person would exercise or use under the circumstances in the conduct of such person’s own affairs. Subject to such provisions, the trustee will be under no obligation to exercise any of the rights or powers vested in it by the indenture at the request or direction of any holder under the indenture, unless such holder will have offered, and if requested, provided, to the trustee security or indemnity satisfactory to the trustee against the losses, liabilities and expenses that might be incurred by it in compliance with such request or direction.

No Personal Liability of Shareholders, Employees, Officers or Directors

No past, present or future shareholder, director, officer or employee, as such, of the Company or any of our predecessors or successors, will have any personal liability for any of our obligations under the notes or the indenture by reason of his, her or its status as such shareholder, director, officer or employee. Each holder of notes by accepting a note waives and releases all such liability. The waiver and release are part of the consideration for the issuance of the notes. Such waiver may not be effective to waive liabilities under the federal securities laws, and it is the view of the SEC that such a waiver is against public policy.

Governing Law

The notes and the indenture are governed by and will be construed in accordance with the laws of the State of New York.

MATERIAL UNITED STATES FEDERAL INCOME TAX CONSIDERATIONS

The following is a summary of certain U.S. federal income tax considerations of the exchange of the outstanding Old Notes for the New Notes pursuant to the exchange offer. It is not a complete analysis of all the potential tax considerations relating to the exchange of outstanding Old Notes for New Notes. This summary is based upon the provisions of the Internal Revenue Code of 1986, as amended (the “Code”), applicable existing and proposed U.S. Treasury Regulations promulgated thereunder, judicial authorities and administrative interpretations, in each case as of the date of this prospectus, all of which are subject to change or different interpretations, possibly with retroactive effect. We cannot assure you that the IRS will not challenge one or more of the tax consequences described in this discussion, and we have not obtained, nor do we intend to obtain, a ruling from the IRS or an opinion of counsel with respect to the U.S. federal income tax considerations of the exchange of the Old Notes for the New Notes.

This discussion is limited to U.S. federal income tax considerations applicable to holders that purchased their Old Notes from us in the initial offering at the initial offering price for cash and who held such Old Notes, and will now hold the New Notes, as “capital assets” within the meaning of Section 1221 of the Code. This discussion does not purport to address all U.S. federal income tax considerations that may be relevant to a holder in light of the holder’s particular circumstances or status, nor does it discuss the U.S. federal income tax considerations to certain types of holders subject to special treatment under the U.S. federal income tax laws, including without limitation, banks, insurance companies, thrifts, other financial institutions, mutual funds, grantor trusts, regulated investment companies, real estate investment trusts, tax-exempt organizations, brokers, dealers or traders in securities, commodities or currencies, United States expatriates, corporations treated as “personal holding companies,” subchapter S corporations, controlled foreign corporations, passive foreign investment companies, persons subject to the alternative minimum tax, traders in securities that elect to use a mark-to-market method of accounting for their securities holdings, United States holders whose functional currency is not the United States dollar, persons that will hold the New Notes as a position in a hedging

transaction, straddle or conversion transaction or as part of a “synthetic security,” other integrated transactions or risk reduction transaction, persons deemed to sell the Old Notes under the constructive sale provisions of the Code, an accrual method taxpayer who is required to recognize income for United States federal income tax purposes no later than when such income is taken into account for financial accounting purposes, a person that purchases or sells notes as part of a wash sale for tax purposes, or entities or arrangements classified as partnerships for United States federal income tax purposes or other pass-through entities, or investors in such entities. Moreover, this discussion does not address the effect of any alternative minimum tax, the Medicare tax on investment income, state, local or non-U.S. tax laws or the application of any U.S. federal taxes other than U.S. federal income taxes (such as U.S. federal estate or gift taxes).

If a partnership (or other entity classified as a partnership for United States federal income tax purposes) holds Old Notes, the tax treatment of a partner generally will depend upon the status of the partner and the activities of the partnership. A partner and the partnership holding the Old Notes should consult their own tax advisors regarding the tax considerations to them of exchanging Old Notes for New Notes in light of their own circumstances.

We believe that the exchange of the Old Notes for the New Notes pursuant to the exchange offer will not be a taxable event for U.S. federal income tax purposes. A holder will not recognize gain or loss upon receipt of a New Note in exchange for an Old Note. The holding period of a New Note will include the holding period of the Old Note exchanged for such New Note, and the initial tax basis of a New Note will be the same as the adjusted tax basis in the exchanged the Old Note immediately before the exchange.

The preceding discussion of certain U.S. federal income tax considerations is for general information only and is not tax advice. Each prospective investor should consult its own tax advisor regarding the particular U.S. federal, state, local and non-U.S. tax considerations of exchanging the Old Notes for the New Notes pursuant to the exchange offer, including the consequences of any proposed change in applicable laws.

PLAN OF DISTRIBUTION

Each broker-dealer that receives New Notes for its own account pursuant to the exchange offer must acknowledge that it will deliver a prospectus in connection with any resale of such New Notes. This prospectus, as it may be amended or supplemented from time to time, may be used by a broker-dealer in connection with resales of New Notes received in exchange for Old Notes where such Old Notes were acquired as a result of market-making activities or other trading activities. We have agreed that, for the one-year period following the consummation of the exchange offer, we will make this prospectus, as amended or supplemented, available to any broker-dealer for use in connection with any such resale. In addition, until the date that is 180 days from the date of the original issuance of the New Notes, all dealers effecting transactions in the New Notes may be required to deliver a prospectus.

We will not receive any proceeds from any sale of New Notes by brokers-dealers. New Notes received by broker-dealers for their own account pursuant to the exchange offer may be sold from time to time in one or more transactions in the over-the-counter market, in negotiated transactions, through the writing of options on the New Notes or a combination of such methods of resale, at market prices prevailing at the time of resale, at prices related to such prevailing market prices or negotiated prices. Any such resale may be made directly to purchasers or to or through brokers or dealers who may receive compensation in the form of commissions or concessions from any such broker-dealer and/or the purchasers of any such New Notes. Any broker-dealer that resells New Notes that were received by it for its own account pursuant to the exchange offer and any broker or dealer that participates in a distribution of such New Notes may be deemed to be an “underwriter” within the meaning of the Securities Act, and any profit of any such resale of New Notes and any commissions or concessions received by

any such persons may be deemed to be underwriting compensation under the Securities Act. The letter of transmittal states that by acknowledging that it will deliver and by delivering a prospectus, a broker-dealer will not be deemed to admit that it is an “underwriter” within the meaning of the Securities Act.

For a period of 180 days following the consummation of the exchange offer, we will promptly send additional copies of this prospectus and any amendment or supplement to this prospectus to any broker-dealer that requests such documents in the letter of transmittal. We have agreed to pay certain expenses incident to the exchange offer and to indemnify the holders of the Old Notes (including any broker-dealers) against certain liabilities, including liabilities under the Securities Act.

LEGAL MATTERS

The validity of the New Notes will be passed upon for us by Luse Gorman, PC, Washington, D.C.

EXPERTS

The consolidated financial statements of Financial Institutions, Inc. and Subsidiaries as of December 31, 2024 and 2023 and for each of the years in the three-year period ended December 31, 2024 and the effectiveness of internal control over financial reporting as of December 31, 2024 incorporated in this Prospectus by reference from the Financial Institutions, Inc. Annual Report on Form 10-K for the year ended December 31, 2024 have been audited by RSM US LLP, an independent registered public accounting firm, as stated in their reports thereon, incorporated herein by reference, and have been incorporated in this Prospectus and Registration Statement in reliance upon such reports and upon the authority of such firm as experts in accounting and auditing.

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 20. Indemnification of Officers and Directors.

The New York Business Corporation Law (the “NYBCL”) permits corporations to limit the liability of directors and to indemnify officers and directors under certain circumstances.

Section Seventh of the Company’s Certificate of Incorporation provide that no director of the Company will be held personally liable to the Company or its shareholders for damages for any breach of duty in his or her capacity as a director unless a judgment or other final adjudication adverse to him or her establishes that (1) his or her acts or omissions were in bad faith or involved intentional misconduct or a knowing violation of law, or (2) he or she personally gained in fact a financial profit or other advantage to which he or she was not legally entitled, or (3) his or her acts violated Section 719 of the Business Corporation Law, governing the liability of directors under certain circumstances.

In the case of any action or proceeding other than in the right of the Company, Article V of the Company’s Bylaws requires the Company to indemnify and hold harmless, to the fullest extent permitted by the NYBCL, any directors and officers who are made a party or threatened to be made a party to an action or proceeding by reason of their service to the Company against expenses actually and reasonably incurred or suffered by such person in connection with such action or proceeding, so long as such person acted in good faith and in a manner such person reasonably believed to be in or not opposed to the best interests of the Company, and, with respect to any criminal proceeding, had no reasonable cause to believe their conduct was unlawful. In the case of any action or proceeding in the right of the Company, the Company must indemnify and hold harmless, to the fullest extent permitted by the NYBCL, any directors and officers who are made a party or threatened to be made a party to an action or proceeding by reason of their service to the Company against expenses actually and reasonably incurred or suffered by such person in connection with such action or proceeding, so long as such person acted in good faith and in a manner such person reasonably believed to be in or not opposed to the best interests of the Company, provided that no indemnification can be made for any claim or matter where such person is adjudged to be liable to the Company, unless and only to the extent that the court determines that, despite the adjudication of liability but in view of all the circumstances of the case, such person is fairly and reasonably entitled to indemnification. The rights of indemnification of directors and officers will also inure to the benefit of their spouses, heirs, executors, administrators and estate.

Directors and officers also have a right to advancement of expenses in defending a proceeding, provided that, so long as such an undertaking is required by the applicable provisions of the NYBCL, the director or officer delivers to the Company an undertaking to repay all advanced amounts if it is ultimately determined by final judicial decision that such person is not entitled to be indemnified. The right to advancement of expenses does not apply to (i) any proceeding brought by the Company and approved by resolution adopted by the affirmative vote of a majority of the total number of authorized directors (whether or not there exist any vacancies in previously authorized directorships at the time such resolution is presented to the Board for adoption) which alleges willful misappropriation of corporate assets by such agent, wrongful disclosure of confidential information, or any other willful and deliberate breach in bad faith of such agent’s duty to the Company or its shareholders, or (ii) any claim for which indemnification is excluded pursuant to the Bylaws.

An “action” or “proceeding” broadly includes any threatened, pending or completed action, suit, investigation (including any internal investigation), inquiry, hearing, mediation, arbitration, other alternative dispute mechanism or any other proceeding, whether civil, criminal, administrative, regulatory, arbitrative, legislative, investigative or otherwise and whether formal or informal, or any related appeal, including an action to enforce a covered person’s rights to indemnification or advancement of expenses under the Bylaws. Indemnifiable and advanceable expenses broadly include all direct and indirect losses, liabilities, damages, expenses, including fees and expenses of attorneys, fees and expenses of accountants, court costs, transcript

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costs, fees and expenses of experts, witness fees and expenses, travel expenses, printing and binding costs, telephone charges, delivery service fees, the premium, security for, and other costs relating to any bond (including cost bonds, appraisal bonds, or their equivalents), judgments, fines, penalties (whether civil, criminal or other), ERISA excise taxes assessed on a person with respect to an employee benefit plan, amounts paid or payable in connection with any judgment, award or settlement, including any interest, assessments, any federal, state, local or foreign taxes, and any state, local and foreign taxes imposed on indemnification payments. Expenses may relate to the investigation, preparation, prosecution, defense, mediation, arbitration, appeal or settlement of a proceeding, or serving as a witness or otherwise participating in a proceeding.

The Bylaws provide that the indemnification rights set forth in the Bylaws are not exclusive of other indemnification rights to which an indemnified party may be entitled under any agreement, vote of shareholders, disinterested directors, other bylaw or otherwise. Except as otherwise required by the NYBCL or the Certificate of Incorporation, the Company will not be obligated to indemnify covered persons under certain circumstances, including if such person receives the indemnification payments from another source (e.g., under an insurance policy), for an accounting or disgorgement of profits pursuant to Section 16(b) of the Exchange Act, or similar provisions of federal, state or local statutory law or common law, for any reimbursement of the Company by such person of any bonus or other incentive-based or equity-based compensation or of any profits realized by such person from the sale of securities of the Company, as required in each case under the Exchange Act, and for any reimbursement of the Company by such person of profits arising from the purchase and sale by such person of securities in violation of Section 306 of the Sarbanes-Oxley Act of 2002.

Pursuant to its Bylaws, the Company must also purchase and maintain insurance to protect itself and its officers and directors against any liability or expense asserted by a covered person in connection with a proceeding.

It is the opinion of the Securities and Exchange Commission that indemnification of directors and officers for liabilities arising under the Securities Act is against public policy and is unenforceable pursuant to Section 14 of the Securities Act.

Item 21. Exhibits and Financial Statement Schedules.

(a) Exhibits:


Number		Description

3.1		Amended and Restated Certificate of Incorporation of Financial Institutions, Inc. (incorporated by reference to Exhibits 3.1, 3.2 and 3.3 to the Company’s Annual Report on Form 10-K for the year ended December 31, 2008 filed March 12, 2009)

3.2		Amended and Restated Bylaws of Financial Institutions, Inc. (incorporated by reference to Exhibit 3.1 to the Company’s Current Report on Form 8-K filed June 25, 2019)

4.1		Indenture, dated as of December 11, 2025, by and between Financial Institutions, Inc. and Wilmington Trust, National Association, as trustee (incorporated by reference to Exhibit 4.1 to the Company’s Current Report on Form 8-K filed December 11, 2025)

4.2		Form of 6.50% Fixed-to-Floating Rate Subordinated Note due 2035 of Financial Institutions, Inc. (incorporated by reference to Exhibit A-2 to the Indenture included as Exhibit 4.1 to the Company’s Current Report on Form 8-K filed December 11, 2025)

5.1		Opinion of Luse Gorman, PC

10.1		Form of Subordinated Note Purchase Agreement, dated as of December 11, 2025, by and between Financial Institutions, Inc. and the several Purchasers (incorporated by reference to Exhibit 10.1 to the Company’s Current Report on Form 8-K filed December 11, 2025)

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Number		Description

10.2		Form of Registration Rights Agreement, dated as of December 11, 2025, by and between Financial Institutions, Inc. and the several Purchasers (incorporated by reference to Exhibit 10.2 to the Company’s Current Report on Form 8-K filed December 11, 2025)

21.1		Subsidiaries of Financial Institutions, Inc. (incorporated by reference to Exhibit 21 to the Company’s Annual Report on Form 10-K for the year ended December 31, 2024 filed March 12, 2025)

23.1		Consent of RSM US LLP

23.2		Consent of Luse Gorman, PC (included in Exhibit 5.1)

24.1		Power of Attorney (included on the signature page to this registration statement)

25.1		Form T-1 Statement of Eligibility under the Trust Indenture Act of 1939, as amended, of Wilmington Trust, National Association, with respect to the Indenture, dated as of December 11, 2025, between Financial Institutions, Inc. and Wilmington Trust, National Association, as trustee, relating to the 6.50% Fixed-to-Floating Rate Subordinated Notes due 2035

99.1		Form of Letter of Transmittal relating to the 6.50% Fixed-to-Floating Rate Subordinated Notes due 2035

107		Filing Fee Table

(b) Financial Statement Schedules:

All schedules for which provision is made in the applicable accounting regulations of the Securities and Exchange Commission have been omitted because they are not required, amounts which would otherwise be required to be shown with respect to any item are not material, are inapplicable or the required information has already been provided elsewhere or incorporated by reference in the registration statement.

Item 22. Undertakings.

(a) The undersigned registrant hereby undertakes:

(1)

To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

(i)

To include any prospectus required by Section 10(a)(3) of the Securities Act of 1933;

(ii)

To reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in the volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Securities and Exchange Commission pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than a 20% change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement); and

(iii)

To include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement.

(2)

That, for the purpose of determining any liability under the Securities Act of 1933, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

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(3) To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

(4) That, for the purpose of determining liability under the Securities Act of 1933 to any purchaser, each prospectus filed pursuant to Rule 424(b) as part of a registration statement relating to an offering, other than registration statements relying on Rule 430B or other than prospectuses filed in reliance on Rule 430A, shall be deemed to be part of and included in the registration statement as of the date it is first used after effectiveness. Provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale before such first use, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately before such date of first use.

(5) That, for the purpose of determining liability of the registrant under the Securities Act of 1933 to any purchaser in the initial distribution of the securities, the undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

(i) Any preliminary prospectus or prospectus of the undersigned registrant relating to the offering required to be filed pursuant to Rule 424;

(ii) Any free writing prospectus relating to the offering prepared by or on behalf of the undersigned registrant or used or referred to by the undersigned registrant;

(iii) The portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and

(iv) Any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

(b) The undersigned registrant hereby undertakes that, for purposes of determining any liability under the Securities Act of 1933, each filing of the registrant’s annual report pursuant to Section 13(a) or Section 15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is incorporated by reference in this registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(c) Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Securities Act of 1933 and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

(d) The undersigned registrant hereby undertakes to respond to requests for information that is incorporated by reference into the prospectus pursuant to Items 4, 10(b), 11 or 13 of this form, within one business day of receipt of such request, and to send the incorporated documents by first class mail or other equally prompt

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means. This includes information contained in documents filed subsequent to the effective date of the registration statement through the date of responding to the request.

(e) The undersigned registrant hereby undertakes to supply by means of a post-effective amendment all information concerning a transaction, and the company being acquired involved therein, that was not the subject of and included in this registration statement when it became effective.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, the registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Warsaw, State of New York, on the 30th day of January, 2026.


		FINANCIAL INSTITUTIONS, INC.

By:		/s/ Martin K. Birmingham
		Martin K. Birmingham
		President and Chief Executive Officer

POWER OF ATTORNEY

Each person whose signature appears below appoints Martin K. Birmingham and W. Jack Plants, II, and each of them, as their true and lawful attorneys-in-fact and agents, with full power of substitution and resubstitution in each, for them and in their name, place and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to this registration statement and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done, as fully to all intents and purposes as they might or would do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them or their substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, as amended, this registration statement has been signed below by the following persons in the capacities indicated on the 30th day of January, 2026.


Signature	Title	Date

/s/ Martin K. Birmingham Martin K. Birmingham	Director, President and Chief Executive Officer (Principal Executive Officer)	January 30, 2026

/s/ W. Jack Plants, II W. Jack Plants, II	Executive Vice President, Chief Financial Officer and Treasurer (Principal Financial Officer)	January 30, 2026

/s/ Sandra A. Byers Sandra A. Byers	Senior Vice President and Controller (Principal Accounting Officer)	January 30, 2026

/s/ Donald K. Boswell Donald K. Boswell	Director	January 30, 2026

/s/ Dawn H. Burlew Dawn H. Burlew	Director	January 30, 2026

/s/ Andrew W. Dorn, Jr. Andrew W. Dorn, Jr.	Director	January 30, 2026

/s/ Robert M. Glaser Robert M. Glaser	Director	January 30, 2026


Signature	Title	Date

/s/ Bruce W. Harting Bruce W. Harting	Director	January 30, 2026

/s/ Susan R. Holliday Susan R. Holliday	Director, Chair	January 30, 2026

/s/ Robert N. Latella Robert N. Latella	Director	January 30, 2026

/s/ Angela J. Panzarella Angela J. Panzarella	Director	January 30, 2026

/s/ Robert L. Schrader Robert L. Schrader	Director	January 30, 2026

/s/ Kim E. VanGelder Kim E. VanGelder	Director	January 30, 2026

/s/ Mark A. Zupan Mark A. Zupan	Director	January 30, 2026

Source: View Original Filing on SEC EDGAR

Financial Institutions, Inc. is offering to exchange up to $80,000,000 of registered 6.50% fixed-to-floating rate subordinated notes due 2035 for any and all outstanding unregistered notes of the same series. The exchange satisfies registration rights from the original December 11, 2025 private placement.

The company will not receive any cash proceeds from the exchange offer. New registered notes are issued solely in exchange for Old Notes, which are then cancelled, so total outstanding indebtedness does not increase and the transaction is effectively a non-cash, administrative refinancing of existing obligations.

The New Notes are identical in material economic terms to the Old Notes but are registered with the SEC, generally free of transfer restrictions, and bear a different CUSIP. Holders of New Notes lose registration rights and related additional-interest protections tied to registration defaults under the prior registration rights agreement.

The notes are unsecured, subordinated obligations that rank below senior indebtedness and are structurally subordinated to subsidiary liabilities, including bank deposits. Risks include floating-rate exposure to Three-Month Term SOFR, potential early prepayment, regulatory capital limits on payments, illiquid trading markets and sensitivity to future credit rating changes.

The notes pay a fixed 6.50% rate initially, then switch on December 15, 2030 to a floating rate equal to Three-Month Term SOFR plus 312 basis points. The floating rate resets quarterly based on the then-current benchmark, so interest payments and market value may fluctuate over the remaining term to 2035.

There is currently no public market for either series, and the company does not expect one to develop or intend to list the notes on any national securities exchange or quotation system. As a result, liquidity may be limited and holders might need to hold to maturity or sell via private transactions.

Financial Institutions, Inc. is a New York financial holding company owning Five Star Bank and Courier Capital. As of September 30, 2025, it reported consolidated assets of $6.29 billion, deposits of $5.36 billion, and shareholders’ equity of $621.7 million, with common stock trading on Nasdaq under the symbol “FISI.”

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