Company: COST
Filing Date: 2025-06-27
Form Type: 11-K
Source: 0000909832-25-000038
Chunk: 5

Company: COSTCO WHOLESALE CORP /NEW
Filing Date: 2025-06-27
Form: 11-K
Chunk 5
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. Employer contributions are allocated based on an employee’s classification as either: covered by the collective bargaining agreements with the International Brotherhood of Teamsters; or other eligible employment.

(1)

#### Covered by the

#### Teamsters Agreements
Eligible employees who have completed one year of service (12 consecutive months) are eligible for an annual employer contribution beginning on the next Plan entry date. Plan entry dates for the employer contribution is the first day of each month. The annual employer contribution is allocated only to the accounts of eligible Plan participants who are employed on the last day of the applicable Plan year. The allocation rate varies, based on years of service, ranging from $0.05 to $0.47 per straight-time hour worked during the Plan year, up to a maximum of 2,080 hours. This annual contribution was $6.3 million for the year ended December 31, 2024, and was deposited into the Plan and allocated to participant accounts in March 2025.

(2)

#### Other eligible employment
The Company matches the lesser of 50% of each employee’s deferral contribution or $500 per year. In addition, eligible employees who have completed one year of service (12 consecutive months) are eligible for an annual discretionary employer contribution beginning on the next Plan entry date. Plan entry dates for the discretionary contribution are the first day of each month. The discretionary contribution is allocated only to the accounts of eligible Plan participants who are employed on the last day of the applicable Plan year. The allocation rate varies, based on years of service, ranging from 4% to 9% of the participant's compensation. This discretionary

<div align='center'>4</div>

#### COSTCO 401(k) RETIREMENT PLAN
<div align='center'>Notes to Financial Statements (Continued)

December 31, 2024 and 2023</div>

contribution was $605.5 million for the year ended December 31, 2024, and was deposited into the Plan and allocated to participant accounts in March 2025.

(c)

#### Participants’ Accounts
Each participant’s account is credited or debited with the participant’s contributions, the Company’s contributions, distributions from the account, earnings and losses, fees, expenses, and changes in underlying account assets. The benefit to which a participant is entitled is their vested account balance.

(d)

#### Vesting
Participants are immediately vested in their deferral contributions and in certain other contributions as defined in the Plan document, adjusted for net value changes