Wash. Rev. Code § 35.34.040
All first and second-class cities and towns are authorized to establish by ordinance a two-year fiscal biennium budget. The ordinance shall be enacted at least six months prior to commencement of the fiscal biennium and this chapter applies to all cities and towns which utilize a fiscal biennium budget. Cities and towns which establish a fiscal biennium budget are authorized to repeal such ordinance and provide for reversion to a fiscal year budget. The ordinance may only be repealed effective as of the conclusion of a fiscal biennium. However, the city or town shall comply with chapter 35.32A or 35.33 RCW, whichever the case may be, in developing and adopting the budget for the first fiscal year following repeal of the ordinance.
RCW 35.34.040