X0508 4 2023-12-19 0000354190 Arthur J. Gallagher & Co. AJG 0001222374 HOWELL DOUGLAS K 2850 GOLF ROAD ROLLING MEADOWS IL 60008-4002 1 VP & Chief Financial Officer 0 Notional Stock Units 0 2023-12-19 4 I 0 4225.2424 224.59 A Common Stock 4225.2424 199570.1524 D Each notional stock unit represents a right to receive one share of Gallagher common stock. The reporting person elected to reallocate amounts previously deferred pursuant to Gallagher's Supplemental Savings and Thrift Plan into the investment option representing Gallagher stock under the plan. As a result, the reporting person is reporting the acquisition of notional stock units. Portions of these notional stock units are payable to the reporting person in shares of common stock in July of 2025, 2026 and 2027 and following the reporting person's separation from service. /s/ Ryan Session, by power of attorney 2023-12-20