Laws – RCWA 59.12.030(3) and RCWA 59.18.057
Notice of Delivery
When complete, the notice should be delivered in person to the tenant. If the tenant is unavailable, leaving the notice with someone else living in the residential unit is allowed but the landlord must also send a copy to the premises by certified mail.
If the tenant and no other individual can be found on the property, the landlord may leave the notice attached to the property in a conspicuous place and also sending a copy by certified mail addressed to the rental unit.