X0508 4 2025-03-31 0000723188 COMMUNITY FINANCIAL SYSTEM, INC. CBU 0001485738 Fesette Neil E. C/O COMMUNITY FINANCIAL SYSTEM, INC. 5790 WIDEWATERS PARKWAY DEWITT NY 13214 1 0 Phantom Stock (Deferred Compensation) 2025-03-31 4 A 0 202.6432 56.75 A Common Stock 202.6432 6903.3714 D 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 will be settled in Community Financial System, Inc. common stock at future dates selected by the reporting person. /s/ Danielle M. Cima, pursuant to a Confirming Statement executed by Neil E. Fesette 2025-03-31