Wash. Rev. Code § 84.52.018
Whenever any property value or claim for exemption or cancellation of a property assessment is appealed to the state board of tax appeals or court of competent jurisdiction and the dollar difference between the total value asserted by the taxpayer and the total value asserted by the opposing party exceeds one-fourth of one percent of the total assessed value of property in the county, the assessor shall use only that portion of the total value which is not in controversy for purposes of computing the levy rates and extending the tax on the tax roll in accordance with this chapter, unless the state board of tax appeals has issued its determination at the time of extending the tax.
When the state board of tax appeals or court of competent jurisdiction makes its final determination, the proper amount of tax shall be extended and collected for each taxing district if this has not already been done. The amount of tax collected and extended shall include interest at the rate of nine percent per year on the amount of the board's final determination minus the amount not in controversy. The interest shall accrue from the date the taxes on the amount not in controversy were first due and payable. Any amount extended in excess of that permitted by chapter 84.55 RCW shall be held in abeyance and used to reduce the levy rates of the next succeeding levy.
RCW 84.52.018