Underinsured Motorist Coverage in Colorado | Conduit Law

Underinsured motorist coverage is first-party auto insurance that pays when the at-fault driver has liability insurance, but not enough to cover your bodily injury. In Colorado it sits inside uninsured motorist coverage under C.R.S. § 10-4-609. It covers the difference between the other driver's liability limits and your damages, up to your UIM limits, and those UIM limits are not reduced by a setoff from other coverage.^{[1]Colorado Revised Statutes § 10-4-609 (2023). " Insurance protection against uninsured motorists - applicability ." Accessed September 13, 2026.}

Key Takeaways

• UIM is your own policy. It responds when the other driver is insured, just not enough.^[1]
• Colorado insurers must offer uninsured motorist coverage in an amount equal to your bodily injury liability limits. You can reject it in writing.^[1]
• Uninsured motorist coverage includes underinsured motorist coverage. One statute, two fact patterns: no insurance, or not enough insurance.^[1]
• The statute says UIM covers the difference between the other driver's liability limits and your damages, up to your UIM maximum, and forbids reducing that coverage by a setoff from liability, MedPay, health insurance, or other UM/UIM.^[1]
• A single-premium endorsement covering multiple vehicles may be limited to applying once per accident. That is a policy-form question, not a slogan.^[1]

How underinsured motorist coverage works

Start with the other driver's bodily injury liability. That policy pays first, up to its limits. If your damages are still higher, your UIM is supposed to cover the gap, up to the UIM limit you bought.^[1]

Two details from the statute matter more than the nickname on the declarations page. First, UIM is not a separate optional product in Colorado. It is uninsured motorist coverage applied to an underinsured vehicle: a land motor vehicle that was insured or bonded for bodily injury at the time of the crash.^[1] Second, the coverage is in addition to legal liability coverage. It is not supposed to shrink because the other driver's insurer already paid something.^[1]

You can decline UM/UIM in writing when the policy is issued. Transportation network company coverage during a prearranged ride is treated differently and cannot be rejected that way.^[1] Rental agreements are outside this section.^[1]

UIM versus UM

Uninsured motorist coverage pays when the at-fault driver has no liability insurance, or is treated as uninsured for the claim (including some hit-and-run and service-of-process problems the statute spells out).^[1] Underinsured motorist coverage is the same first-party coverage when that driver has a policy, just not enough of one.

People search both names. In Colorado they are one statutory package. The hire-intent pages stay separate: uninsured motorist claims in Denver and Kansas UM claims. This page is the Colorado definition and the gap math.

Example

These numbers are illustrative, not a case result. Suppose the at-fault driver carries Colorado-minimum bodily injury limits and tenders $25,000 per person. Your damages, if proved, are $80,000. You carried $100,000 in UM/UIM and did not reject it in writing.

Under C.R.S. § 10-4-609(1)(c), UIM covers the difference between the liability limits and the damages, up to your UIM maximum, and the UIM available is not reduced by a setoff from that liability payment.^[1] The working gap in that hypo is $55,000, well inside a $100,000 UIM limit. Change the damages, the other driver's limits, or your own limit, and the gap moves. That is why the declarations page and the crash facts both matter.

The thing people get wrong

Older policy forms, and a lot of national explainers, still talk as if Colorado UIM is a setoff product: take your UIM limit, subtract what the other driver paid, and that remainder is all you can ever collect. Current Colorado law says the opposite for coverage issued under this section: the amount available is not reduced by a setoff from legal liability insurance, medical payments, health insurance, or other uninsured or underinsured coverage.^[1]

If someone is still running setoff math on a post-2008 Colorado policy, they are reading a form the statute already answered. Read the statute and the declarations page together. Do not assume a blog from another state.

Policy limits, stacking, and one accident

The insurer must offer UM/UIM equal to your bodily injury liability limits. It does not have to offer more than those liability limits.^[1] After you choose limits or decline, the insurer does not have to keep re-offering at every renewal unless you ask in writing for more.^[1]

Stacking is the fight over whether more than one UIM limit applies to the same crash. The statute allows a single policy or endorsement, issued for a single premium covering multiple vehicles, to be limited to applying once per accident.^[1] Whether two different policies in the same household can both respond is a different question. It turns on the forms, the named insureds, and the facts. It is not a multiplier you apply because it would be convenient.

Unreasonable delay

UIM is a first-party claim against your own insurer. If payment of benefits is unreasonably delayed or denied, Colorado provides a statutory action for reasonable attorney fees and court costs and two times the covered benefit.^{[2]Colorado Revised Statutes § 10-3-1116 (2023). " Remedies for unreasonable delay or denial of benefits ." Accessed September 13, 2026.} That multiplier is not automatic. It is a remedy for unreasonable delay or denial, on top of other claims the law already allows.^[2]

Frequently Asked Questions

Is underinsured motorist coverage required in Colorado?

It must be offered. You can reject uninsured motorist coverage in writing, with a narrow exception for certain transportation-network coverage during a prearranged ride.^[1]

Does UIM pay if the other driver has insurance?

Yes. That is the point of underinsured coverage. Uninsured motorist coverage includes damage you are legally entitled to collect from the owner or driver of an underinsured motor vehicle.^[1]

Does the other driver's payment reduce my UIM limits?

The statute says the amount of coverage available under this section shall not be reduced by a setoff from legal liability insurance or several other listed coverages.^[1] UIM still covers the difference between those liability limits and your damages, up to your UIM maximum.

Is UIM the same as bodily injury liability?

No. Bodily injury liability pays other people when you are at fault. UIM pays you (and other insureds on your policy) when someone else is at fault and their insurance is short.

Should I cash the at-fault driver's policy before opening UIM?

Not as a reflex. UIM is tied to what you are legally entitled to recover and to how the two coverages interact. Signing a release on the liability claim without looking at the UIM claim can create a problem the statute does not fix for you. A free consult is how you sequence it.

The Bottom Line

Underinsured motorist coverage is the gap-filler on your own auto policy when the at-fault driver was insured, just not enough. Colorado writes that gap into uninsured motorist coverage, forbids the old setoff shrink, and still leaves the real work on the declarations page, the damages, and the timing of any release. None of that is a settlement number. If you were hurt in a Colorado crash and the other driver's limits look thin, a free consultation is how you find out what your own policy actually says.

Related: Denver uninsured motorist claims, Kansas UM claims, bodily injury liability, and our Denver car accident lawyer page.

General information about Colorado insurance coverage, not legal advice. Reading this does not create an attorney-client relationship. Coverage, stacking, and timing depend on the policy, the facts, and attorney review.