(1) Service of the mandatory benefits assignment order on the department is invalid unless it is served with four answer forms in conformance with RCW
41.50.610, together with stamped envelopes addressed to, respectively, the clerk of the court where the order was issued, the obligee's attorney or the obligee, and the obligor at the last mailing address known to the obligee. The obligee shall also include an extra copy of the mandatory benefits assignment order for the department to mail to the obligor. Service on the department shall be in person or by any form of mail requiring a return receipt.
(2) On or before the date of service of the mandatory benefits assignment order on the department, the obligee shall mail or cause to be mailed by certified or registered mail a copy of the mandatory benefits assignment order to the obligor at the obligor's last mailing address known to the obligee; or, in the alternative, a copy of the mandatory benefits assignment order shall be served on the obligor in the same manner as a summons in a civil action on, before, or within two days after the date of service of the order on the department. This requirement is not jurisdictional, but if the copy is not mailed or served as this subsection requires, or if any irregularity appears with respect to the mailing or service, the superior court, in its discretion, may quash the mandatory benefits assignment order, upon motion of the obligor promptly made and supported by an affidavit showing that the obligor has been prejudiced due to the failure to mail or serve the copy.