X0508 4 2024-01-12 0 0000909832 COSTCO WHOLESALE CORP /NEW COST 0001928633 Frates Caton 999 LAKE DRIVE ISSAQUAH WA 98027 0 1 0 0 Executive Vice President 0 Common Stock 2024-01-12 4 A 0 30.744 0.00 A 7460.559 D Represents additional restricted stock units ("RSUs") resulting from the upward adjustment of outstanding unvested RSUs by a factor of 1.018, in connection with the special cash dividend payable by the issuer on January 12, 2024. The adjustment was required under applicable plan documents. The additional RSUs reported are subject to the same vesting schedules as the original unvested RSUs to which they relate. Not applicable. Grant of Restricted Stock Units. /s/ Alejandro Torres, Attorney-in-Fact 2024-01-12