Wash. Rev. Code § 84.56.340
Any person desiring to pay taxes upon any part or parts of real property heretofore or hereafter assessed as one parcel, or tract, or upon such person's undivided fractional interest in such a property, may do so by applying to the county assessor, who must carefully investigate and ascertain the relative or proportionate value said part or part interest bears to the whole tract assessed, on which basis the assessment must be divided, and the assessor shall forthwith certify such proportionate value to the county treasurer: PROVIDED, That excepting when property is being acquired for public use, or where a person or financial institution desires to pay the taxes and any penalties and interest on a mobile home upon which they have a lien by mortgage or otherwise, no segregation of property for tax purposes shall be made under this section unless all current year and delinquent taxes and assessments on the entire tract have been paid in full. The county treasurer, upon receipt of certification, shall duly accept payment and issue receipt on the apportionment certified by the county assessor. In cases where protest is filed to said division appeal shall be made to the county legislative authority at its next regular session for final division, and the county treasurer shall accept and receipt for said taxes as determined and ordered by the county legislative authority. Any person desiring to pay on an undivided interest in any real property may do so by paying to the county treasurer a sum equal to such proportion of the entire taxes charged on the entire tract as interest paid on bears to the whole.
RCW 84.56.340
Applicability-1996 c 153: See note following RCW 84.56.020.