Wash. Rev. Code § 70.47.070
The benefits available under the basic health plan shall be excess to the benefits payable under the terms of any insurance policy issued to or on the behalf of an enrollee that provides payments toward medical expenses without a determination of liability for the injury. Except where in conflict with federal or state law, the benefits of any other health plan or insurance which covers an enrollee shall be determined before the benefits of the basic health plan. The *administrator shall require that managed health care systems conduct and report on coordination of benefits activities as provided under this section.
RCW 70.47.070
*Reviser's note: The definition of "administrator" was changed to "director" in RCW 70.47.020 by 2011 1st sp.s. c 15 s 83.