RCW 4.16.150: Action on mutual open accounts.

In an action brought to recover a balance due upon a mutual open and current account, where there have been reciprocal demands between the parties, the cause of action shall be deemed to have accrued from the time of the last item proved in the account on either side, but whenever a period of more than one year shall have elapsed between any of a series of items or demands, they are not to be deemed such an account.