X0508 4 2025-07-31 0000354190 Arthur J. Gallagher & Co. AJG 0001222374 HOWELL DOUGLAS K 2850 GOLF ROAD ROLLING MEADOWS IL 60008-4002 1 VP & Chief Financial Officer 0 Common Stock 2025-07-31 4 M 0 35739.4628 0 A 117776.7558 D Common Stock 3165 I By Spouse Common Stock 418.691 I Gallagher 401(k) plan account Notional Stock Units 0 2025-07-31 4 M 0 35739.4628 0 D Common Stock 35739.4628 177994.9726 D The reporting person has no voting or invesment power over these shares and disclaims beneficial ownership. 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 2024, 2025, 2026, 2028 and 2029 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 2025 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/ Monica Norzagaray, by power of attorney 2025-08-04