Wash. Rev. Code § 84.64.040
The county prosecuting attorney shall furnish to holders of certificates of delinquency, at the expense of the county, forms of applications for judgment and forms of notice and summons when the same are required, and shall prosecute to final judgment all actions brought by holders of certificates under the provisions of this chapter for the foreclosure of tax liens, when requested so to do by the holder of any certificate of delinquency: PROVIDED, Said holder has duly paid to the clerk of the court the sum of two dollars for each action brought as per RCW 84.64.120: PROVIDED, FURTHER, That nothing herein shall be construed to prevent said holder from employing other and additional counsel, or prosecuting said action independent of and without assistance from the prosecuting attorney, if he or she so desires, but in such cases, no other and further costs or charge whatever shall be allowed than the costs provided in this section and RCW 84.64.120: AND PROVIDED, ALSO, That in no event shall the county prosecuting attorney collect any fee for the services herein enumerated.
RCW 84.64.040