NB Bancorp director updates insider share holdings

NB Bancorp, Inc. director Christopher R. Lynch filed an amended insider report updating his share holdings.

Rhea-AI Filing Summary

NB Bancorp, Inc. director Christopher R. Lynch filed an amended insider report updating his share holdings. The filing shows he holds 96,922 shares of common stock directly and 60,000 shares indirectly through an IRA. These amounts include restricted stock that vests 20% per year starting on April 24, 2026, and additional restricted shares that vest fully on January 2, 2027.

The amendment notes that an earlier Form 4 filed on April 27, 2026 mistakenly reported a sale of common stock that did not actually occur, and the beneficial ownership figures have been corrected accordingly.

Insider Trade Summary

2 transactions reported

Mixed 2 txns

Insider Lynch Christopher R.

Role Director

Type	Security	Shares	Price	Value
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 96,922 shares (Direct); Common Stock — 60,000 shares (Indirect, By IRA)

Footnotes (3)

1. F1. Includes shares of restricted stock which vest at a rate of 20% per year commencing on April 24, 2026.
2. F2. Includes shares of restricted stock which vest 100% on January 2, 2027.
3. F3. On April 27, 2026, a Form 4 was mistakenly filed reporting a disposition of shares of common stock that did not in fact occur. The change in the securities beneficially owned has been corrected accordingly in this amended Form 4.

Key Figures

Direct common shares: 96,922 shares Indirect IRA shares: 60,000 shares Vesting start date: April 24, 2026 +2 more

5 metrics

Direct common shares 96,922 shares Directly held following correction

Indirect IRA shares 60,000 shares Held indirectly through IRA

Vesting start date April 24, 2026 Restricted stock vesting 20% per year

Cliff vest date January 2, 2027 Restricted stock vests 100% on this date

Unknown transactions 2 entries Classified as holding entries in summary

Key Terms

restricted stock, beneficially owned, Form 4, IRA

4 terms

restricted stock financial

"Includes shares of restricted stock which vest at a rate of 20% per year"

Shares granted to an individual that carry limits on transfer or sale until certain conditions are met, such as staying with the company for a set time or hitting performance targets. Think of them as a locked gift that gradually opens; for investors they matter because they affect how many shares may enter the market later, signal management incentives and potential dilution, and reveal confidence in future company performance.

beneficially owned financial

"The change in the securities beneficially owned has been corrected accordingly"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

Form 4 regulatory

"On April 27, 2026, a Form 4 was mistakenly filed reporting a disposition"

Form 4 is a official document that company insiders, such as executives or major shareholders, file with regulators whenever they buy or sell company shares. It provides transparency about how those with inside knowledge are trading, helping investors see if insiders are confident in the company's prospects or may be selling for personal reasons. This information can influence investor decisions by revealing insiders' perspectives on the company's value.

IRA financial

"direct_or_indirect: "I", nature_of_ownership: "By IRA""

An individual retirement account (IRA) is a savings account designed to help people put aside money for their retirement, often with tax advantages that encourage long-term savings. It matters to investors because it can grow over time, providing financial security later in life, and offers benefits that can reduce current taxes or allow investments to compound more effectively.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What does the NB Bancorp (NBBK) amended Form 4/A report for Christopher R. Lynch?

The amended Form 4/A updates Christopher R. Lynch’s reported holdings in NB Bancorp common stock. It corrects a prior mistaken sale entry and now reflects his current direct and indirect ownership, including restricted stock scheduled to vest over 2026 and 2027.

How many NB Bancorp (NBBK) shares does Christopher R. Lynch now report owning?

The filing reports 96,922 NB Bancorp common shares held directly and 60,000 shares held indirectly through an IRA. These totals include restricted stock awards that are subject to scheduled vesting on April 24, 2026 and January 2, 2027.

What error does the NB Bancorp (NBBK) Form 4/A correct?

The amendment corrects a prior Form 4 filed on April 27, 2026 that mistakenly reported a disposition of NB Bancorp common stock. The filing states that this sale never occurred and updates the beneficially owned share amounts accordingly.

How do Christopher R. Lynch’s restricted NB Bancorp (NBBK) shares vest?

One block of restricted NB Bancorp stock vests 20% each year starting April 24, 2026. Another restricted award vests 100% on January 2, 2027. Both awards are included in the updated ownership totals disclosed in the amended filing.

Does the NB Bancorp (NBBK) Form 4/A show new insider buying or selling?

The Form 4/A does not show new buying or selling activity. Instead, it revises previously reported beneficial ownership after clarifying that a disposition reported on April 27, 2026 did not actually occur, and updates Lynch’s share counts.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 05/15/2026 - 11:15 AM EDT Learn about SEC filing dates

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Lynch Christopher R.

(Last) (First) (Middle)

1063 GREAT PLAIN AVE

(Street)

NEEDHAM MASSACHUSETTS 02492

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
NB Bancorp, Inc. [ NBBK ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
04/24/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)
04/27/2026

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock								96,922(1)(2)(3)	D
Common Stock								60,000	I	By IRA

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Includes shares of restricted stock which vest at a rate of 20% per year commencing on April 24, 2026.

2. Includes shares of restricted stock which vest 100% on January 2, 2027.

3. On April 27, 2026, a Form 4 was mistakenly filed reporting a disposition of shares of common stock that did not in fact occur. The change in the securities beneficially owned has been corrected accordingly in this amended Form 4.

	/s/ Steven T. Lanter, pursuant to power of attorney	05/15/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)