Underinsured and Uninsured Motorist Coverage (UM)

Legal Terms Explained: Underinsured and Uninsured Motorist Coverage (UM)

Uninsured motorist (UM) and underinsured motorist (UIM) coverage is part of your own auto policy, and it pays for your injuries when the at-fault driver either has no liability insurance at all or carries limits too low to cover your damages. UM also typically applies in hit-and-run crashes where the other driver is never identified. It is one of the most misunderstood — and most valuable — coverages on an auto policy.

The basic split

• Uninsured motorist (UM) applies when the at-fault driver has no liability coverage, or in a qualifying hit-and-run.
• Underinsured motorist (UIM) applies when the at-fault driver has some coverage, but your damages exceed their policy limits.

Some states require insurers to offer one or both; others make them optional. Either way, the coverage follows you as an injured person, not just your car — in most policies it also protects you as a passenger or pedestrian.

A worked example

Suppose you are rear-ended at a stoplight and seriously hurt. Your total damages come to $110,000: $60,000 in medical bills, $20,000 in lost wages, and $30,000 in pain and suffering. The at-fault driver carries a state-minimum policy with $25,000 in bodily injury liability limits. You carry $100,000 in UIM coverage.

1. The at-fault driver's insurer pays out its full $25,000 limit. That is all that policy will ever pay, no matter how severe your injuries are.
2. You then make a UIM claim with your own insurer for the shortfall.
3. How much UIM money is available depends on your state. In a reduced-by (offset) state, your UIM limit is reduced by what the liability carrier paid: $100,000 minus $25,000 leaves $75,000 available, for a total recovery of $100,000 — still $10,000 short of your damages. In an excess (add-on) state, your full $100,000 sits on top of the liability payment, so the entire remaining $85,000 is covered.

Same crash, same policy limits, meaningfully different outcomes. This is why an attorney's first question in a serious crash is often about your declarations page, not the other driver's.

Stacking

Many states permit stacking — combining UM/UIM limits across vehicles or policies. If you insure two cars on one policy with $50,000 of UM coverage each, stacking can turn that into $100,000 of available coverage for a single crash. Whether stacking is allowed, and whether you paid for it, varies by state and policy language.

Three traps worth knowing

The consent-to-settle clause. Most UIM policies require you to get your own insurer's written permission before accepting the at-fault driver's policy limits. Settling without consent can void your UIM claim, because it destroys the insurer's subrogation rights — its ability to chase the at-fault driver for reimbursement.

Your insurer is now your adversary. A UM/UIM claim is a contract claim against your own carrier, and the carrier can dispute fault and damages just as the other driver's insurer would. If it unreasonably refuses to pay a clear claim, that can give rise to a separate bad faith claim in many states.

Deadlines differ. Because the claim arises from your insurance contract rather than the crash itself, the limitations period and the policy's notice requirements may differ from the ordinary personal injury statute of limitations. Late notice is a common reason claims get denied.

The practical takeaway: state-minimum liability limits are low almost everywhere, and a meaningful share of drivers carry no insurance at all. UM/UIM is the coverage that protects you from other people's bad decisions, and raising it is usually cheap relative to what it can pay.

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