Wash. Rev. Code § 86.09.508
A redemption of the property sold may be made by the owner or any person on behalf and in the name of the owner or by any party in interest at any time before deed issues, by paying the amount of the purchase price and interest as in this chapter provided, and the amount of any assessments which such purchaser may have paid thereon after purchase by him or her and during the period of redemption in this section provided, together with like interest on such amount, and if the district is the purchaser, the redemptioner shall not be required to pay the amount of any district assessment levied subsequent to the assessment for which said land was sold, but all subsequent and unpaid assessments levied upon said land to the date of such redemption shall remain a lien and be payable and the land be subject to sale and redemption at the times applicable to such subsequent annual district assessment. Redemption must be made in legal tender, as provided for the collection of state and county taxes, and the county treasurer must credit the amount paid to the person named in the certificate and pay it on demand to such person or his or her assignees. No redemption shall be made except to the county treasurer of the county in which the land is situated.
RCW 86.09.508