Wash. Rev. Code § 30A.44.180
Whenever any bank shall voluntarily liquidate, any dividends to depositors or other creditors of such bank remaining uncalled for and unpaid at the conclusion of the liquidation shall be transmitted to the director and shall be deposited by him or her in a bank or trust company to his or her credit in trust for the benefit of the persons entitled thereto, and shall be paid by him or her to them upon receipt of satisfactory evidence of their right thereto.
All moneys so deposited remaining unclaimed for five years after deposit shall escheat to the state for the benefit of the permanent school fund and shall be paid by the director into the state treasury. It shall not be necessary to have the escheat adjudged in a suit or action.
RCW 30A.44.180