Washington Revised Code Title 4. Civil Procedure § 4.16.040. Actions limited to six years

(1) An action upon a contract in writing, or liability express or implied arising out of a written agreement, except as provided for in RCW 64.04.007(2).

(2) An action upon an account receivable. For purposes of this section, an account receivable is any obligation for payment incurred in the ordinary course of the claimant's business or profession, whether arising from one or more transactions and whether or not earned by performance.

(3) An action for the rents and profits or for the use and occupation of real estate.