Wash. Rev. Code § 9A.56.078
(2)
(b)
(ii) After performing service under (b)(i) of this subsection, the plaintiff shall promptly send notice of service under (b)(i) of this subsection and a copy of the summons or process to the defendant by registered mail, with return receipt requested, to the defendant's last known address. After complying with this subsection (2)(b)(ii), the plaintiff shall file the following with the secretary of state to be attached to the summons or process filed under (b)(i) of this subsection:
[ 2007 c 393 s 1.]