Wash. Rev. Code § 85.24.180
If any of the installment of taxes are not paid as herein provided, the county treasurer shall sell all lots or parcels of land on which taxes have been levied and assessed, whether in the name of the designated owner or the name of an unknown owner, to satisfy all delinquent and unpaid assessments, interest, penalties, and costs. The treasurer must commence the sale of property upon which taxes are delinquent within sixty days after the same become delinquent, and continue such sale from day to day thereafter until all the lots and parcels of land upon which taxes have not been paid are sold. Such sales shall take place at the front door of the courthouse. The proper treasurer shall give notice of such sales by publishing a notice thereof once a week for two successive weeks in two or more newspapers published within the district, or if no such newspaper is published, within the district, then within any two or more newspapers having a general circulation in such district; such notice shall contain a list of all lots and parcels of land upon which such assessments are delinquent, with the amount of interest, penalty, and cost at the date of sale, including costs of advertising had upon each of such lots, pieces, or parcels of land, together with the names of the owners thereof, if known to the treasurer, or the word "unknown" if unknown to the treasurer, and shall specify the time and place of sale, and that the several lots or parcels of land therein described, or so much as may be necessary, will be sold to satisfy the assessment, interest, penalty, and cost due upon each. All such sales shall be made between the hours of ten o'clock a.m. and three o'clock p.m. Such sales shall be made in the manner now prescribed by the general laws of this state for the sale of property for delinquent taxes, and certificates and deeds shall be made to the purchasers and redemptions made as is now prescribed by the general laws of this state in the manner and upon the terms therein specified: PROVIDED, That no tax deeds shall be made until after the expiration of one year after the issuance of the certificate, and during such year any person interested may redeem. A certificate of purchase shall be issued to the district for all lots and parcels of land not sold. Certificates issued to the district shall be delivered to the board of commissioners of the district. The board of commissioners of the district may sell and transfer any such certificate to any person who is willing to pay to the district the amount for which the lot or parcel of land therein described was stricken off to the district, with the interest subsequently accrued thereon. Within ten days after the completion of sale of all lots, pieces, and parcels of land authorized to be sold as aforesaid, the treasurer must make a return to the board of commissioners with a statement of the doings thereon, showing all lots and parcels of land sold by him or her, to whom sold and the sum paid therefor. The purchaser at improvement sales acquires a lien on the lot, piece, or parcel of land sold for the amount paid by him or her at such sales for all delinquent taxes and assessments, and all costs and charges thereon, whether levied previously or subsequently to such sale, subsequently paid by him or her on the lot or parcel of land, and shall be entitled to interest thereon at the rate of ten percent per annum from the date of such payment.
RCW 85.24.180