Washington Revised Code Title 12. District Courts--Civil Procedure § 12.08.060. Pleading account or instrument

When the cause of action, or setoff, arises upon an account or instrument for the payment of money only, it shall be sufficient for the party to deliver the account or instrument, or a copy thereof, to the court, and to state that there is due to him or her thereon, from the adverse party, a specified sum, which he or she claims to recover or setoff. The court may, at the time of pleading, require that the original account, or instrument, be exhibited to the inspection of the adverse party, with liberty to copy the same; or if not so exhibited, may prohibit its being given in evidence.