[Form 4] COMMUNITY FINANCIAL SYSTEM, INC. Insider Trading Activity

Rhea-AI Filing Summary

Community Financial System, Inc. President & CEO Karaivanov Dimitar reported equity compensation activity in company common stock. On March 4, 2026, a three-year performance-based restricted stock award granted in 2023 vested at the target level, resulting in 4,698 shares plus 526.2062 dividend reinvestment shares, totaling 5,224.2062 shares acquired at no stated price. To cover tax obligations from this vesting, 2,825.2062 shares were disposed of at $59.87 per share through a tax-withholding transaction. Following these changes, direct ownership was 23,657 shares, and an additional 3,271.3426 shares were held indirectly through the company’s 401(k) plan based on a current plan statement.

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

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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^*

Karaivanov Dimitar

(Last) (First) (Middle)

C/O COMMUNITY FINANCIAL SYSTEM, INC.

333 BUTTERNUT DRIVE

(Street)

SYRACUSE NY 13214

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
COMMUNITY FINANCIAL SYSTEM, INC. [ CBU ]

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

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

3. Date of Earliest Transaction (Month/Day/Year)
03/04/2026

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

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

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

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	03/04/2026		A		5,224.2062(1)	A	$0	26,482.2062	D
Common Stock	03/04/2026		F(2)		2,825.2062	D	$59.87	23,657	D
Common Stock								3,271.3426	I	By 401(k) Plan(3)

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. On March 4, 2026, the Compensation Committee approved the vesting of the three-year performance-based restricted stock award, granted to the reporting person in 2023, based on achievement of predetermined performance criteria at the target level. The reporting person received 4,698 shares of common stock under the award and 526.2062 shares of common stock acquired under the dividend reinvestment feature of the Community Financial System, Inc. 2022 Long-Term Incentive Plan, as amended (the "Plan").

2. Payment of tax liability associated with vesting of performance stock award.

3. The number of shares reported herein acquired pursuant to Community Financial System, Inc.'s 401(k) Plan and are based on a current plan statement.

	/s/ Danielle M. Cima, pursuant to a Confirming Statement executed by Dimitar Karaivanov	03/06/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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FAQ

What insider transactions did CBU President & CEO Karaivanov Dimitar report?

Karaivanov Dimitar reported a performance-based restricted stock award vesting into 4,698 shares plus 526.2062 dividend reinvestment shares, and a related tax-withholding disposition of 2,825.2062 shares at $59.87 per share, all in Community Financial System, Inc. common stock.

How many CBU shares did the CEO acquire from the performance award vesting?

The CEO acquired 4,698 shares from a three-year performance-based restricted stock award granted in 2023, plus 526.2062 additional shares through the dividend reinvestment feature of the Community Financial System, Inc. 2022 Long-Term Incentive Plan, totaling 5,224.2062 shares.

Why were some CBU shares disposed of in this Form 4 filing?

The filing states that 2,825.2062 shares of Community Financial System, Inc. common stock were disposed of to pay tax liabilities associated with the vesting of the performance stock award, at a reported price of $59.87 per share, characterized as a tax-withholding disposition.

What is Karaivanov Dimitar’s direct and indirect CBU share ownership after these transactions?

After the reported transactions, direct ownership stood at 23,657 shares of Community Financial System, Inc. common stock, while 3,271.3426 additional shares were held indirectly through the company’s 401(k) plan, with the indirect amount based on a current plan statement.

What plan governed the CBU performance-based restricted stock award?

The performance-based restricted stock award, including 4,698 shares plus 526.2062 dividend reinvestment shares, was granted under the Community Financial System, Inc. 2022 Long-Term Incentive Plan, as amended, which provided both performance vesting conditions and a dividend reinvestment feature for the CEO’s award.