Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 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 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES 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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1. Name and Address of Reporting Person * Pecor Raymond C III 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 _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O COMMUNITY FINANCIAL SYSTEM, INC., 5790 WIDEWATERS PARKWAY 3. Date of Earliest Transaction (Month/Day/Year) 03/17/2026 (Street) DEWITT, NY 13214 4. If Amendment, Date 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 (City) (State) (Zip) 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 10,185.221(1) D Common Stock 11,277.977(2) I By Trust(3)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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 Underlying Securities (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 of Derivative Security: 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

Phantom Stock (Deferred Compensation under Merchants plan)

(4)

(4)

(4)

Common Stock

10,088.6702

10,088.6702(5)

D

Phantom Stock (Deferred Compensation)

(6)

(6)

(6)

Common Stock

8,798.5926

8,798.5926(7)

D

Phantom Stock (Deferred Stock Units)

(8)

03/17/2026

A

1,220

(8)

(8)

Common Stock

1,220

$ 0

8,390.6624(9)

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Pecor Raymond C III C/O COMMUNITY FINANCIAL SYSTEM, INC. 5790 WIDEWATERS PARKWAY DEWITT, NY 13214	X

Signatures

/s/ Danielle M. Cima, pursuant to a Confirming Statement executed by Raymond C. Pecor, III		03/19/2026
**Signature of Reporting Person		Date

Explanation of Responses:

*	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).
(1)	Includes 78.04 shares acquired on January 12, 2026 pursuant to the Community Financial System, Inc. Dividend Reinvestment Plan.
(2)	Includes 86.2 shares acquired on January 12, 2026 pursuant to the Community Financial System, Inc. Dividend Reinvestment Plan.
(3)	The reporting person disclaims beneficial ownership of these securities, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of all of the reported shares for purposes of Section 16 or any other purpose.
(4)	The units of phantom stock were acquired through Merchants Bancshares, Inc.'s ("Merchants") deferred compensation plan. Each unit of phantom stock is the economic equivalent of one share of Community Financial System, Inc. common stock. The units of phantom stock relating to such deferred compensation plan will be settled in Community Financial System, Inc. common stock at future dates selected by the reporting person.
(5)	Includes 77.299 units of phantom stock acquired on January 12, 2026 under the Merchants' deferred compensation plan's dividend reinvestment feature
(6)	Each unit of phantom stock is the economic equivalent of one share of Community Financial System, Inc. common stock. The units of phantom stock relating to the Deferred Compensation Plan for Directors (the "DCP for Directors"), will be settled in Community Financial System, Inc. common stock at future dates selected by the reporting person.
(7)	Includes 67.3778 units of phantom stock acquired as dividend equivalents on January 12, 2026 under the DCP for Directors.
(8)	The reporting person has received deferred stock units under the Community Financial System, Inc. 2022 Long-Term Incentive Plan, as amended (the "LTIP"). Each phantom stock unit which represents a deferred stock unit is the economic equivalent of one share of Community Financial System, Inc. common stock and will be settled in common stock at a predetermined date.
(9)	Includes 55.1073 units of phantom stock acquired on January 12, 2026 under the LTIP's dividend reinvestment feature.

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