Wash. Rev. Code § 84.68.020
In all cases of the levy of taxes for public revenue which are deemed unlawful or excessive by the person, firm or corporation whose property is taxed, or from whom such tax is demanded or enforced, such person, firm or corporation may pay such tax or any part thereof deemed unlawful, under written protest setting forth all of the grounds upon which such tax is claimed to be unlawful or excessive; and thereupon the person, firm or corporation so paying, or their legal representatives or assigns, may bring an action in the superior court or in any federal court of competent jurisdiction against the state, county or municipality by whose officers the same was collected, to recover such tax, or any portion thereof, so paid under protest: PROVIDED, That RCW 84.68.010 through 84.68.070 shall not be deemed to enlarge the grounds upon which taxes may now be recovered: AND PROVIDED FURTHER, That no claim need be presented to the state or county or municipality, or any of their respective officers, for the return of such protested tax as a condition precedent to the institution of such action.
RCW 84.68.020