Wash. Rev. Code § 83.100.160
Upon filing findings under RCW 83.100.150, the clerk of the superior court shall give notice of the filing by causing notice thereof to be posted at the courthouse in the county in which the court is located. In addition, the department of revenue shall give notice of the filing to all persons interested in the proceeding by mailing a copy of the notice to all persons having an interest in property subject to the tax. The department of revenue is not required to conduct a search for persons interested in the proceedings or property. The department of revenue must mail a copy of the notice only to persons of whom the department has received actual notice as having an interest in the proceeding or property, and, if a probate or administrative proceeding has been commenced in this state, to persons who are listed in the court file as having an interest in the proceedings or property.
RCW 83.100.160