AJG Arthur J Gallagher and Company

EXPLANATORY NOTE

Arthur J. Gallagher  & Co. (the “Registrant” or “we”) registered, pursuant to a Registration Statement on Form S-8 filed on August 6, 2014 (Registration No. 333-197898) (the “Initial 2014 Plan Registration Statement”), 9,150,000 shares of our Common Stock, par value $1.00 per share (“Common Stock”), under the Arthur J. Gallagher  & Co. 2014 Long-Term Incentive Plan (the “2014 Plan”). We subsequently filed a Post-Effective Amendment No. 1 to the Initial 2014 Plan Registration Statement (the “2014 Post-Effective Amendment” and together with the Initial 2014 Plan Registration Statement, the “2014 Plan Registration Statement”) to reflect that any shares of Common Stock which may have become issuable in connection with outstanding awards under the 2014 Plan that were forfeited, settled in cash, cancelled or expired after May 16, 2017 would instead become eligible for issuance under the Arthur J. Gallagher & Co. 2017 Long-Term Incentive Plan (the “2017 Plan” and together with the 2014 Plan, the “Prior Plans”) and that such shares of Common Stock available for issuance under the Initial 2014 Plan Registration Statement would no longer be issued under the 2014 Plan and would instead be issuable under the 2017 Plan. We also registered, pursuant to a Registration Statement on Form S-8 filed on November 1, 2017 (Registration No. 333-221274) (the “2017 Plan Registration Statement”), 16,000,000 shares of Common Stock, under the 2017 Plan.

Our board of directors approved the Arthur J. Gallagher & Co. 2022 Long-Term Incentive Plan (the “2022 Plan”) on March 10, 2022 and such plan was subsequently approved by our stockholders on May 10, 2022. Pursuant to the terms of the 2022 Plan, the following shares of Common Stock will be issuable under the 2022 Plan: (i) 13,500,000 shares of Common Stock plus (ii) the number of shares of Common Stock subject to any awards granted under the Prior Plans that are outstanding as of May 10, 2022 that are subsequently settled for cash, forfeited, expired, or for any reason are cancelled or terminated.

Pursuant to the undertakings in Item 9 of the Initial 2014 Plan Registration Statement and Item 9 of the 2017 Plan Registration Statement, we are filing this Post-Effective Amendment No. 2 to the 2014 Plan Registration Statement and Post-Effective Amendment No. 1 to the 2017 Plan Registration Statement to provide that such registration statements shall also cover the following shares of Common Stock that will become eligible for issuance under the 2022 Plan: (i) the 718,250 shares of Common Stock subject to any awards granted under the 2014 Plan that are outstanding as of May 10, 2022 that are subsequently settled for cash, forfeited, expired, or for any reason are cancelled or terminated and (ii) the 10,529,336 shares of Common Stock subject to any awards granted under the 2017 Plan that are outstanding as of May 10, 2022 that are subsequently settled for cash, forfeited, expired, or for any reason are cancelled or terminated.