Stacked vs. Unstacked UM/UIM Coverage in Colorado

By the FigureMyTax Editorial Team · How we calculate

Stacking adds the uninsured and underinsured motorist limits of several vehicles or policies together. In Colorado the statute lets a single-premium multi-vehicle policy be limited to once per accident, so your policy wording decides.

What stacking means

Many auto policies list a UM/UIM limit for each insured vehicle, and a household may hold several policies. Stacking adds those limits together after one injury, so $100,000 on each of three vehicles becomes $300,000. Unstacked coverage pays only one limit. It matters only when your damages exceed the at-fault driver's liability limits and a single UM/UIM limit.

How Colorado treats it

C.R.S. 10-4-609(1)(c) says UM/UIM coverage is in addition to the other driver's liability coverage and covers the difference between that coverage's limits and your damages, up to your limit. It also says that a single policy or endorsement issued for a single premium covering multiple vehicles may be limited to applying once per accident. The statute does not say how separate policies combine.

A worked Colorado example

Suppose you carry $100,000 of UIM, covering three vehicles under one policy for one premium, your damages are $250,000, and the at-fault driver has a $25,000 liability limit. The gap is $225,000. If the policy says its coverage applies once per accident, the most it pays is $100,000. If it says nothing like that, coverage for each vehicle may apply and the ceiling would be $300,000, so you could reach the full $225,000. Try your own numbers in the Colorado UM/UIM stacking calculator.

Your other coverage does not reduce it

The statute also says the amount of coverage available shall not be reduced by a setoff from any other coverage, including legal liability insurance, medical payments coverage, health insurance or other UM/UIM insurance. So your health insurer's payments, or your own medical payments coverage, do not shrink the UM/UIM you can claim.

What to check

Look at your declarations page for the number of vehicles and the limit, and read the UM/UIM and "other insurance" sections for language limiting you to one coverage. See what subsection (1)(c) says and what it leaves open and how UM and UIM work together in Colorado.

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.