Does Colorado Allow UM/UIM Stacking? The Statute and the Cases

By the FigureMyTax Editorial Team · How we calculate

Colorado's statute lets a single-premium, multi-vehicle policy be limited to applying once per accident and bars setoffs from other coverage, including other UM/UIM. How separate policies combine is left to their wording.

The statutory text

Section 10-4-609(1)(c), added in 2007, says the coverage is in addition to any legal liability coverage and covers the difference, if any, between the limits of that liability coverage and the damages sustained, excluding exemplary damages, up to the maximum coverage obtained. A single policy or endorsement issued for a single premium covering multiple vehicles may be limited to applying once per accident. And the amount of coverage available shall not be reduced by a setoff from any other coverage, including liability insurance, medical payments coverage, health insurance or other UM/UIM insurance.

What the statute does not say

It does not say whether coverage under separate policies, or under one policy with separate premiums, can be added together, and it does not prohibit stacking. The first sentence limits what a single-premium policy may do; the setoff sentence limits what an insurer may subtract.

What court summaries report

Annotations to the statute, published by a Colorado legal-reference site and a law-firm compilation, report decisions holding that anti-stacking provisions in underinsured motorist policies do not violate the statute's public policy and that a claimant could not stack the UIM benefits of three separate policies, and that anti-stacking provisions do not include exclusions or "other insurance" clauses. We did not read those opinions, so treat them as leads and confirm with an attorney.

The 2026 Supreme Court decision

In USAA v. Wenzell (2026 CO 25), decided April 27, 2026, the Colorado Supreme Court explained that section 10-4-609(1)(c) provides that insurers shall not reduce coverage by a setoff from "other uninsured or underinsured motor vehicle insurance," so primary and excess UIM insurers are equally prevented from using setoffs tied to payments from underlying coverage. It held that an excess UIM insurer's exhaustion clause is enforceable only when exhaustion is based on the policyholder's undisputed damages. It did not decide whether policies can be stacked.

How to use this

Compare the single-limit and combined-limit outcomes in the Colorado UM/UIM stacking calculator, start with the plain-English stacked versus unstacked explainer, and read how UM and UIM work together.

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