X0508 4 2024-06-20 0000723188 COMMUNITY FINANCIAL SYSTEM, INC. CBU 0001475265 Pecor Raymond C III C/O COMMUNITY BANK SYSTEM, INC. 5790 WIDEWATERS PARKWAY DEWITT NY 13214 1 0 Phantom Stock (Deferred Compensation) 2024-06-20 4 A 0 479.7865 44.03 A Common Stock 479.7865 7486.2609 D Each unit of phantom stock is the economic equivalent of one share of Community Bank System, Inc. common stock. The units of phantom stock relating to the Deferred Compensation Plan will be settled in Community Bank System, Inc. common stock at future dates selected by the reporting person. /s/ Danielle M. Cima, pursuant to a Confirming Statement executed by Raymond C. Pecor, III 2024-06-21