Uninsured / Underinsured Motorist (UM/UIM)

Quick answer

What does Uninsured / Underinsured Motorist (UM/UIM) mean?

Uninsured/underinsured motorist (UM/UIM) coverage helps pay your injuries or damages when the at-fault driver has little or no insurance. Rules vary by state for stacking and offset. Related: /guides/auto-stacked-unstacked-um-uim-buying-guide; /claims/guides/auto-uninsured-motorist-claim-guide. Editor-reviewed mid-July 2026.

How it works

In auto insurance policies, uninsured / underinsured motorist (um/uim) is usually defined in the contract rather than in marketing copy. Read the exact wording, then check whether the term changes your deductible, covered causes of loss, documentation burden, or claim payout.

Example and common mistake

Example

Before choosing a policy, compare how uninsured / underinsured motorist (um/uim) appears in the declarations page, coverage form, and exclusions. Small wording differences can change the claim result.

Common mistake

Do not assume uninsured / underinsured motorist (um/uim) means the same thing across carriers. Confirm the limit, trigger, waiting period, or proof requirements before relying on a quote.

Related terms

Auto Insurance

First Notice of Loss (FNOL)

First notice of loss (FNOL) is your initial report to the insurer after an incident. Prompt FNOL preserves evidence, starts mitigation duties, and avoids late-report denials. Get a claim number in writing. Related: /claims/guides/auto-accident-claim-guide-2026; /claims/guides/home-water-damage-claim-guide. Editor-reviewed mid-July 2026.

Read definition

Auto Insurance

Liability Limit

Liability limits cap what your insurer pays for bodily injury or property damage you cause to others. State minimums are often below the assets many households need to protect. Compare umbrella or higher limits before binding. Related: /guides/auto-um-uim-coverage-deep-guide-2026; hub /insurance/auto. Editor-reviewed mid-July 2026.

Read definition

Common questions

What does Uninsured / Underinsured Motorist (UM/UIM) mean in auto insurance?

Uninsured/underinsured motorist (UM/UIM) coverage helps pay your injuries or damages when the at-fault driver has little or no insurance. Rules vary by state for stacking and offset. Related: /guides/auto-stacked-unstacked-um-uim-buying-guide; /claims/guides/auto-uninsured-motorist-claim-guide. Editor-reviewed mid-July 2026.

Why does Uninsured / Underinsured Motorist (UM/UIM) matter?

Uninsured / Underinsured Motorist (UM/UIM) can affect what is covered, how much you pay out of pocket, and what evidence you need when comparing policies or filing a claim.

What should I check before buying coverage involving Uninsured / Underinsured Motorist (UM/UIM)?

Check the policy wording, limits, exclusions, waiting periods, deductibles, and claim documentation rules tied to Uninsured / Underinsured Motorist (UM/UIM).

Related concepts to compare: First Notice of Loss (FNOL), Liability Limit.