Uninsured/Underinsured Motorist Coverage
Uninsured/Underinsured Motorist (UM/UIM) coverage is an auto insurance policy that pays for your medical expenses, lost wages, and other damages if you're hit by a driver who has no insurance (uninsured) or not enough insurance (underinsured) to cover the costs.
Definition maintained by the InsurTool Editorial Team. Last reviewed .
Quick Summary
Uninsured/Underinsured Motorist (UM/UIM) coverage protects you if you’re in an accident with a driver who has no insurance or insufficient insurance to cover your damages. Required in many states, it ensures you’re not left paying out of pocket for injuries caused by uninsured drivers. Use our Auto Insurance Calculator to see how UM/UIM coverage fits into your policy.
What is Uninsured/Underinsured Motorist Coverage?
In plain English: Uninsured/Underinsured Motorist Coverage is a specific part of how insurance works. The best way to think about insurance is that it’s a way to share financial risk — you pay a smaller amount regularly, and the insurance company helps cover bigger costs if something goes wrong. Uninsured/Underinsured Motorist Coverage describes one particular piece of that system.
How UM/UIM Coverage Works
Uninsured Motorist (UM)
Covers you when the at-fault driver has no auto insurance at all. This includes hit-and-run accidents where the driver flees the scene and cannot be identified.
Underinsured Motorist (UIM)
Covers you when the at-fault driver has insurance, but their liability limits are too low to cover all your damages. UIM pays the difference between the other driver’s coverage and your actual expenses.
| Coverage Type | What It Pays For | Required? |
|---|---|---|
| Liability | Damage and injuries you cause to others | Yes (in most states) |
| Collision | Damage to your car from crashes | No (but lenders often require it) |
| Comprehensive | Damage from theft, weather, vandalism | No |
| Uninsured Motorist | Damage from drivers without insurance | Varies by state |
| PIP (Personal Injury Protection) | Your medical bills after an accident | Required in no-fault states |
What UM/UIM Coverage Covers
- Bodily Injury — Medical expenses, lost wages, and pain and suffering for you and your passengers.
- Hit-and-Run Accidents — Coverage when the at-fault driver flees the scene and cannot be found.
- Underinsured Drivers — Coverage when the other driver’s insurance is insufficient.
- Property Damage — In some states, covers damage to your vehicle from uninsured drivers.
Why UM/UIM Coverage is Important
According to the Insurance Information Institute, approximately 1 in 8 drivers in the U.S. is uninsured. Without UM/UIM coverage, you could be stuck paying medical bills and other expenses out of pocket if you’re hit by an uninsured driver. Even if the driver has insurance, their coverage limits may not be enough to cover serious injuries.
Coverage Limits
UM/UIM limits are typically expressed the same way as liability limits (e.g., 100/300/100):
- First number: Maximum per person for bodily injury
- Second number: Maximum per accident for bodily injury
- Third number: Maximum per accident for property damage (if included)
Experts recommend matching your UM/UIM limits to your liability limits for full protection. Our calculator can help you determine the right limits.
Frequently Asked Questions (FAQ)
Is UM/UIM coverage required by law?
UM/UIM is required in 20 states and the District of Columbia. In other states, it’s optional but highly recommended. Even when optional, many insurers include it unless you specifically reject it in writing.
Does UM/UIM cover hit-and-run accidents?
Yes, UM coverage typically covers hit-and-run accidents, as long as you file a police report and can’t identify the other driver.
What’s the difference between UM and UIM?
UM covers accidents with drivers who have no insurance. UIM covers accidents with drivers who have insurance but not enough to cover all damages.
Can I stack UM/UIM coverage?
Stacking allows you to combine coverage from multiple vehicles or policies. Some states allow stacking, which can increase your coverage limits notably.
Authoritative Sources
- Insurance Information Institute (III) - Uninsured/Underinsured Motorist Coverage
- National Association of Insurance Commissioners (NAIC) - Auto Insurance Guide
- State Farm - Uninsured Motorist Coverage Guide
- IRS (Internal Revenue Service) - Tax rules for business use of vehicles
- NHTSA (National Highway Traffic Safety Administration) - U.S. auto safety standards
Related Terms
Liability Coverage Personal Injury Protection No-Fault Insurance Claims
About this definition
Written and checked against the primary sources linked on this page by the InsurTool Editorial Team. Definitions describe how these terms are used in the United States; policy wording differs between insurers, and state law changes the meaning of some terms. Your own policy document is the authority for your coverage.
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