X0508 4 2024-03-19 0000723188 COMMUNITY BANK SYSTEM, INC. CBU 0001264816 STEELE SALLY A C/O COMMUNITY BANK SYSTEM, INC. 5790 WIDEWATERS PARKWAY DEWITT NY 13214 1 0 Common Stock 33628 D Common Stock 4585 I Joint with brother Phantom Stock (Deferred Stock Units) 2024-03-19 4 A 0 1395 0 A Common Stock 1395 2597.5975 D The reporting person's directly owned shares have been reduced by 6.3782 shares to adjust for fractional shares that were reported as acquired by the reporting person but were paid out in cash. The fractional shares were included in previous filings made to report distributions of deferred stock units and deferred compensation. The reporting person has received deferred stock units under the Community Bank System, Inc. 2022 Long-Term Incentive Plan, as amended (the "Plan"). Each phantom stock unit which represents a deferred stock unit is the economic equivalent of one share of Community Bank System, Inc. common stock and will be settled in common stock at a predetermined date. Includes 10.235, 11.527, 12.417, and 10.6404 units of phantom stock acquired on April 10, 2023, July 10, 2023, October 10, 2023, and January 10, 2024, respectively, as dividend equivalents under the Plan. /s/ Danielle M. Cima, pursuant to a Confirming Statement executed by Sally A. Steele 2024-03-21