X0306 4 2022-07-15 0000354190 Arthur J. Gallagher & Co. AJG 0001222374 HOWELL DOUGLAS K 2850 GOLF ROAD ROLLING MEADOWS IL 60008-4002 1 VP & Chief Financial Officer Common Stock 2022-07-15 4 M 0 24331 0 A 94123.062 D Notional Stock Units 0 2022-07-15 4 M 0 24331 0 D Common Stock 24331 194480.56 D Each notional stock unit represents a right to receive one share of Gallagher common stock. Portions of these notional stock units are payable to the reporting person in shares of common stock in July of 2022, 2023, 2025 and 2026 and following the reporting person's separation from service. This report discloses the distribution of notional stock units (representing equity compensation previously deferred by the reporting person in the Arthur J. Gallagher & Co. Supplemental Savings and Thrift Plan) in the form of Gallagher common stock. The timing of this distribution in July 2022 is in accordance with the terms of the Supplemental Savings and Thrift Plan and the reporting person's election at the time of deferral. /s/ Seth Diehl, by power of attorney 2022-07-19