X0508 4 2025-03-31 0000723188 COMMUNITY FINANCIAL SYSTEM, INC. CBU 0001738659 Singh Savneet C/O COMMUNITY FINANCIAL SYSTEM, INC. 5790 WIDEWATERS PARKWAY DEWITT NY 13214 1 0 Deferred Stock (Deferred Compensation) 2025-03-31 4 A 0 308.37 56.75 A Common Stock 308.37 308.37 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 Confirming Statement executed by Savneet Singh 2025-03-31