RCW 48.14.070

In event any person has paid to the commissioner any tax, license fee or other charge in error or in excess of that which he or she is lawfully obligated to pay, the commissioner shall upon written request make a refund thereof. A person may only request a refund of taxes within six years of the end of the calendar year for which the taxes are owed. A person may only request a refund of fees or charges other than taxes within 13 months of the date the fees or charges were paid. Refunds may be made either by crediting the amount toward payment of charges due or to become due from such person, or by making a cash refund.