Enrolling Family Members

To enroll family member(s) for coverage you must first access the enrollment website and enroll the family member(s). You then must provide additional documentation to support your relationship to that person. For example if you are adding your spouse you must provide a copy of the state certified marriage certificate.

We also require additional declarations of eligibility for Domestic Partners and children for whom you serve as Legal Guardian. These required forms will be mailed to you when you make this election on the enrollment website. Click here to view a complete list of eligible family members and the documents we require or refer to the Summary of Benefits. Click here to access all of the declaration forms or visit your location’s Payroll Clerk.

You may submit your certificates and additional forms in any of the following ways:

  • By intercompany mail to: Location 99 – Attn:  Employee Benefit Department
  • By fax to: 425-427-3069
  • By US Mail to: 

Costco Wholesale                                                                                                                              ATTN: Employee Benefit Department                                                                              PO Box34195                                                                                                                   Seattle, WA 98124-1195

Payroll deductions will begin immediately but this does not guarantee coverage. Coverage for your eligible family members will not take effect until you have submitted all of the required certificates, declarations and documentation.