The bill amends existing law (RCW 48.43.600) to change time limits and procedures for when health carriers may request refunds from health care providers for previously paid claims. It requires carriers to make refund requests in writing and to state why they believe a refund is owed, and in coordination-of-benefits cases to include the name and mailing address of the entity with primary payment responsibility. General deadlines are: carriers must request refunds within 12 months after the original payment (6 months for mental health and substance use disorder services); for coordination-of-benefits situations the deadlines are 18 months (9 months for mental health and substance use disorder services). A provider must contest a refund request in writing within 30 days of receipt or the request is deemed accepted and the refund must be paid; if a refund is contested, the carrier may not demand payment sooner than six months after the carrier’s request was received. The amendment also says a carrier may request a refund at any time if a third party (including a government entity) is legally responsible for the claim and the carrier cannot recover directly because the third party has paid or will pay the provider. If a provider-carrier contract conflicts with this section, the statute prevails, but providers may voluntarily refund at any time. The section excludes dental-only health carriers, Title XVIII (Medicare) services, and Medicare supplemental plans regulated under chapter 48.66 RCW. Section 1 of the act is effective January 1, 2027. This is a procedural change to an existing statute (not the creation of a new crime or penalty); it modifies deadlines, notice and contest procedures, and coordination-of-benefits requirements for refund requests. The text refers to the definition of “mental health and substance use disorder services” in RCW 48.43.766, but that definition and earlier statutory language or broader enforcement provisions are not included in the provided facts.

If enacted, carriers will have firm, shorter windows to ask providers to return overpayments and must make those requests in writing with reasons and, in coordination-of-benefits cases, the primary payer’s contact information. Providers will face a real cash-flow and administrative risk: they must put written challenges in place within 30 days or the refund request is treated as accepted and cannot be pressed for payment sooner than six months after the carrier’s request if contested. Mental health and substance use disorder providers are likely to be most affected because carriers get shorter timeframes to make refund requests for those services, and coordination-of-benefits timing differs from general claims. Carriers gain clearer authority to seek refunds from providers (including anytime a third party is found legally responsible but has paid the provider), but they lose flexibility to override these timelines by contract, so both sides will need new procedures to meet deadlines. The effective date is January 1, 2027. Important details are missing here, including the exact statutory definition of mental health and substance use disorder services and any enforcement or appeals process beyond the 30-day contest rule, so some operational impacts depend on those unanswered specifics.