RCW 59.18.063: Landlord—Written receipts for payments made by tenant.

(1) A landlord must accept a personal check, cashier's check, or money order for any payment of rent made by a tenant, except that a landlord is not required to accept a personal check from any tenant that has had a personal check written to the landlord or the landlord's agent that has been returned for nonsufficient funds or account closure within the previous nine months. A landlord must also allow for the tenant to submit a rental payment by mail unless the landlord provides an accessible, on-site location. (2) A landlord may refuse to accept cash for any payment of rent made by a tenant, but shall provide a receipt for any payment made by a tenant in the form of cash when the landlord accepts cash. (3) A landlord shall provide, upon the request of a tenant, a written receipt for any payments made by the tenant in a form other than cash.