First-Party Protection

Understanding Uninsured & Underinsured Motorist Coverage

Published: August 16, 2026 • 7 min read • NAIC & State Statute Sourced

Uninsured Motorist (UM) and Underinsured Motorist (UIM) coverage protects you, your passengers, and resident family members when an at-fault driver either carries no auto liability insurance or carries limits too low to cover your medical bills, lost wages, and permanent disability.

According to the Insurance Research Council (IRC), approximately 1 in 8 drivers nationwide is uninsured. In some states (such as Florida, Mississippi, and Michigan), the uninsured rate exceeds 20% to 25%. Without UM/UIM on your declaration page, you are left paying for your own medical recovery or suing an insolvent driver in court.

1. UM vs. UIM: How the Two Coverages Operate

Uninsured Motorist (UM)

Applies when you are struck by a driver who has no active insurance policy, a driver whose insurance was cancelled for non-payment, an unpermitted driver, or a hit-and-run driver who flees the scene.

Underinsured Motorist (UIM)

Applies when an at-fault driver has insurance, but their bodily injury limit (e.g. $25,000) is lower than your total hospital bills ($80,000). Your UIM policy pays the remaining $55,000 difference up to your UIM cap.

2. Stacked vs. Non-Stacked UM Limits Explained

In states that allow stacking (such as Florida, Pennsylvania, and Nevada), you can multiply your UM coverage across vehicles:

Example: A 2-Vehicle Household with $100k/$300k UM Limits

• Non-Stacked Policy: Maximum payout in an accident is $100,000 per person.

• Stacked Policy (2 Cars): Total available coverage becomes $200,000 per person ($100,000 × 2).

3. Uninsured Motorist Property Damage (UMPD) vs. Collision

Standard UM coverage only pays for medical trauma and bodily injury. If an uninsured driver smashes into your car:

With Collision Coverage: Your insurer pays for your car repairs minus your collision deductible, regardless of whether the driver is insured.
With UMPD Coverage: Pays for your vehicle damage up to the UMPD limit (e.g. $25,000) with a low or zero deductible, but only if the at-fault driver is positively identified as uninsured.

Watch Out for Omitted UM/UIM on Online Quotes

Because UM/UIM can add $15 to $35 per month to a premium, online quote comparison tools frequently deselect UM/UIM coverage to make their quotes look cheaper. Always verify that UM/UIM is active before binding.

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Frequently Asked Questions

What is Uninsured Motorist (UM) coverage on an auto insurance policy?

Uninsured Motorist (UM) coverage pays for medical expenses, lost wages, pain and suffering, and funeral costs for you and your passengers if you are injured in an accident caused by a driver who has no liability insurance or in a hit-and-run collision where the driver cannot be identified.

What is the difference between Uninsured Motorist (UM) and Underinsured Motorist (UIM)?

Uninsured Motorist (UM) applies when the at-fault driver has zero insurance coverage. Underinsured Motorist (UIM) applies when the at-fault driver has insurance, but their policy limits are too low to pay for your total medical and lost wage damages.

What is the difference between stacked and unstacked UM coverage?

Stacked UM coverage allows you to combine the uninsured motorist limits across multiple vehicles on your policy (or across multiple policies in your household) to increase your total available protection in a severe accident. Non-stacked UM restricts coverage to the limit assigned to the single vehicle involved in the crash.

Does Uninsured Motorist cover damage to my vehicle?

Standard UM Bodily Injury (UMBI) only covers physical injuries. To cover vehicle repairs caused by an uninsured driver, you must have either Uninsured Motorist Property Damage (UMPD) or Collision coverage on your declaration page.