Wash. Rev. Code § 19.09.305
When an entity registered under this chapter, or its president, treasurer, or comparable officers, cannot be found after reasonably diligent effort, the secretary of state must be an agent of such entity upon whom process may be served. Service on the secretary must be made by delivering to the secretary or the secretary's designee duplicate copies of such process, and a filing fee to be established by rule of the secretary. Thereupon, the secretary must immediately cause one of the copies to be forwarded to the registrant at the most current address shown in the secretary's files. Any service on the secretary must be returnable in not less than thirty days.
Any fee under this section may be taxable as costs in the action.
The secretary must maintain a record of all process served on the secretary under this section, and must record the date of service and the secretary's action.
Nothing in this section limits or affects the right to serve process required or permitted to be served on a registrant in any other manner now or hereafter permitted by law.
RCW 19.09.305