X0609 4 2026-10-22 0000909832 COSTCO WHOLESALE CORP /NEW COST 0002076006 Barbre Tiffany Marie false 999 LAKE DRIVE ISSAQUAH WA 98027 1 Principal Accounting Officer 0 Common Stock 2026-10-22 4 A 0 1965 0 A 7120.448 D Common Stock 2026-10-22 4 F 0 90.23 1018.21 D 7030.218 D Common Stock 2026-10-22 4 F 0 93.948 1018.21 D 6936.27 D Common Stock 2026-10-22 4 F 0 101.536 1018.21 D 6834.734 D Common Stock 2026-10-22 4 F 0 84.603 1018.21 D 6750.131 D Common Stock 2026-10-22 4 F 0 166.451 1018.21 D 6583.68 D Common Stock 2.1788 I By 401(k) Grant of Restricted Stock Units. Vests one-fifth on October 22, 2027, and one-fifth annually on October 22 for the following four years. In addition, under the 2019 Stock Incentive Plan, this grant is eligible for accelerated vesting upon the anniversary of the reporting person's 25th, 30th and 35th years of service. Not applicable. Grant of Restricted Stock Units. This transaction is a withholding by the Company for taxes in connection with the vesting of previously granted restricted stock units. The price represents the closing market price of Costco common stock on Nasdaq on October 22, 2026. /s/ Alejandro Torres, Attorney-in-Fact 2026-10-26