X0508 5 2023-12-31 0 1 0000723188 COMMUNITY BANK SYSTEM, INC. CBU 0001475265 Pecor Raymond C III C/O COMMUNITY BANK SYSTEM, INC. 5790 WIDEWATERS PARKWAY DEWITT NY 13214 1 0 Common Stock 2023-06-21 4 G 0 L 330 0 A 9182.8993 D Common Stock 9293.05 I By Trust Includes 256.956 shares acquired pursuant to the Community Bank System, Inc. Dividend Reinvestment Plan. Includes 267.115 shares acquired pursuant to the Community Bank System, Inc. Dividend Reinvestment Plan. 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. /s/ Danielle M. Cima, pursuant to a Confirming Statement executed by Raymond C. Pecor, III 2024-02-14