Does Washington Allow UIM Stacking? What RCW 48.22.030 Says

By the FigureMyTax Editorial Team · How we calculate

RCW 48.22.030 lets a Washington policy cap total underinsured coverage at the higher of the applicable limits and define its limit per accident. It does not set a mandatory rule on stacking, so your policy language decides.

Required coverage

RCW 48.22.030(2) and (3) requires underinsured, hit-and-run and phantom vehicle coverage in new and renewal policies for vehicles registered or principally garaged in Washington, in the same amount as your liability coverage unless you reject it. Umbrella and excess-only policies are not covered by the requirement.

Rejection

A named insured or spouse may reject underinsured coverage in writing. A rejection does not carry into a later supplemental or renewal policy unless a named insured or spouse later requests the coverage in writing.

Policy clauses

Subsection (5) lets the policy treat its limit as the maximum for one accident regardless of the number of covered persons, claims, vehicles or premiums. Subsection (6) lets it provide that total limits from other similar insurance cannot exceed the higher of the applicable limits.

Definitions

A vehicle is underinsured when no liability coverage applies, or when the sum of the liability limits applicable to you after the accident is less than the damages you are legally entitled to recover. A phantom vehicle requires corroboration beyond the insured's own testimony and a report to law enforcement within 72 hours.

How to use this

Compare the results in the Washington UIM stacking calculator, start with the plain-English stacked versus single-limit explainer, and read how Washington UIM works.

This is general information, not legal advice, and the state comparisons above are illustrative, not an exhaustive survey. Confirm how Washington's rules apply to your specific case with a licensed Washington attorney.