Wash. Rev. Code § 89.30.649
It shall be the duty of the county treasurer of the county in which any land in the general improvement or divisional district is located, to furnish upon request of the owner or any person interested, a statement showing any and all assessments levied as shown by the assessment roll in his or her office upon land described in such request and all statements of general taxes covering any land in such district shall be accompanied by a statement showing the condition of district assessments against such lands: PROVIDED, That the failure of the county treasurer to render any statement herein required of him or her, shall not render invalid any assessments made for any general improvement or divisional district or proceeding had for the enforcement and collection of such assessments pursuant to this chapter.
RCW 89.30.649