X0306 4 2021-03-16 0000723188 COMMUNITY BANK SYSTEM, INC. CBU 0001485739 Whipple John F. C/O COMMUNITY BANK SYSTEM, INC. 5790 WIDEWATERS PARKWAY DEWITT NY 13214 1 Phantom Stock (Deferred Stock Units) 0 2021-03-16 4 A 0 569 0 A Common Stock 569 569 D Phantom Stock (Deferred Compensation) Common Stock 10790.6837 10790.6837 D The reporting person has received deferred stock units under the Community Bank System, Inc. 2014 Long-Term Incentive 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. 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. Includes 66.8943 units of phantom stock acquired on January 11, 2021 under the Deferred Compensation Plan's dividend reinvestment feature. /s/ Danielle M. Cima, pursuant to a Confirming Statement executed by John F. Whipple, Jr. 2021-03-17