(1) A responsible parent shall make all support payments through the office of support enforcement or the Washington state support registry if:
(a) The parent's support order contains a provision directing the parent to make support payments through the office of support enforcement or the Washington state support registry; or
(b) If the parent has received written notice from the office of support enforcement under RCW
26.23.110,
74.20A.040, or
74.20A.055 that all future support payments must be made through the office of support enforcement or the Washington state support registry.
(2) A responsible parent who has been ordered or notified to make support payments to the office of support enforcement or the Washington state support registry shall not receive credit for payments which are not paid to the office of support enforcement or the Washington state support registry unless:
(a) The department determines that the granting of credit would not prejudice the rights of the residential parent or other person or agency entitled to receive the support payments and circumstances of an equitable nature exist; or
(b) A court, after a hearing at which all interested parties were given an opportunity to be heard, on equitable principles, orders that credit be given.
(3) The rights of the payee under an order for support shall not be prejudiced if the department grants credit under subsection (2)(a) of this section. If the department determines that credit should be granted pursuant to subsection (2) of this section, the department shall mail notice of its decision to the last known address of the payee, together with information about the procedure to contest the determination.