What UM and UIM coverage pay for
Uninsured and underinsured motorist coverages protect you and your passengers when the driver who caused the crash can't pay:
- Uninsured motorist bodily injury (UM or UMBI) pays for medical bills, lost wages and, depending on the state, pain and suffering when an at-fault driver has no liability insurance. In many states it also applies to hit-and-run crashes.
- Underinsured motorist bodily injury (UIM) pays when the at-fault driver has insurance, but their limits are too low to cover your losses.
- Uninsured motorist property damage (UMPD), offered in some states, pays for damage to your car caused by an uninsured driver.
UM and UIM usually protect you even when you're a passenger in someone else's car, a pedestrian or a cyclist, depending on your policy and state.
Why it matters
The Insurance Research Council estimates that roughly 15% of U.S. drivers are uninsured, and that about one in three drivers are either uninsured or underinsured. The share varies a lot by state, and you can see each state's estimate on its page in our state directory.
Underinsurance matters as much as no insurance. Many drivers carry only their state's minimum liability limits, which can be quickly used up by a hospital stay. Without UIM, you might be left to rely on health insurance, which may have deductibles and doesn't replace lost income, or to sue the at-fault driver personally, who may not have the assets to pay.
UM and UIM also fill gaps that other coverages leave. Collision pays to fix your car but nothing for your injuries. MedPay and PIP pay medical bills but usually have modest limits and don't compensate for pain and suffering. Uninsured and underinsured motorist coverage is designed to stand in for the liability insurance the other driver should have had.
Is uninsured motorist coverage required?
Triple-I reports that uninsured motorist coverage is mandatory in about 20 jurisdictions. In most other states, insurers must offer it, and you can decline only by signing a written rejection. A few states require UIM as well, or require that UM limits match your liability limits unless you choose lower limits in writing.
Before signing a rejection form to save money, consider what you'd rely on if a driver with no insurance seriously injured you. Check your state's requirements with the coverage checker, and see our guide to minimum car insurance requirements.
UM property damage vs. collision
| Feature | UM property damage | Collision |
|---|---|---|
| When it pays | Only when an identified uninsured driver is at fault | Any crash, regardless of fault |
| Hit-and-run | Often excluded or limited, depending on the state | Usually covered |
| Deductible | May have a small deductible, set by state rules or the policy | Your chosen collision deductible |
| Availability | Only in some states | Available everywhere as an option |
If you already carry collision, UMPD may mainly help by lowering your out-of-pocket cost. If you carry liability only, UMPD can be an inexpensive way to get some protection for your car.
Stacked vs. unstacked coverage
Some states let you "stack" uninsured and underinsured motorist limits. Stacking combines the limits for each vehicle on your policy, or across policies, into a larger total.
| Illustration: $50,000 UM limit, three cars on the policy | Unstacked | Stacked |
|---|---|---|
| Most available for one injured person | $50,000 | Up to $150,000 |
| Premium | Lower | Higher |
Pennsylvania is a clear example. Its Insurance Department explains that stacked coverage applies unless you reject it in writing, that stacking multiplies your UM and UIM limit by the number of vehicles on the policy, and that rejecting stacking lowers your premium. Other states limit or prohibit stacking, and policy language matters, so ask your insurer how it works where you live.
How to choose UM and UIM limits
- Many drivers match UM and UIM limits to their own liability limits, and some states require insurers to offer matching limits.
- Think about your health insurance deductible, your income and how long you could go without working.
- If you have several cars and live in a stacking state, compare the cost of stacked and unstacked options.
- Because UM protects you rather than others, it's often one of the better-value coverages to keep when trimming a budget.
To see how coverage levels change an estimate, use the premium estimator.
How a UM or UIM claim works
- Report the crash to police, especially for a hit-and-run. Many policies require prompt police reporting for hit-and-run claims.
- Notify your insurer quickly and collect the other driver's details if you have them.
- For UIM, you usually must first claim against the at-fault driver's liability coverage. Tell your insurer before accepting that settlement, since many policies require consent.
- Your insurer steps into the other driver's shoes. It evaluates fault and damages as the at-fault driver's insurer would, which can make UM claims adversarial.
- Disputes may go to arbitration or court depending on your policy and state.
For the broader claim process, see what happens after a car accident. For medical coverage that pays regardless of fault, see PIP and medical payments.
Hit-and-run crashes
Many states treat an unidentified hit-and-run driver as an uninsured motorist for bodily injury claims. Rules for proof differ: some policies or states require evidence such as physical contact with the other vehicle or an independent witness, especially when the other car never touched yours. Damage to your car in a hit-and-run is usually paid under collision rather than UMPD. Report the crash to police promptly, photograph the scene and gather witness information to protect your claim.
Frequently asked questions
What does uninsured motorist coverage cover?
It pays for injuries to you and your passengers caused by an at-fault driver with no insurance, and in many states by a hit-and-run driver. Some states also offer UM property damage for your car.
What is the difference between uninsured and underinsured motorist coverage?
Uninsured coverage applies when the at-fault driver has no insurance. Underinsured coverage applies when they have insurance, but their limits are too low to cover your losses.
Is uninsured motorist coverage required?
Triple-I reports it's mandatory in about 20 jurisdictions. In most other states, insurers must offer it and you must reject it in writing if you don't want it.
What does stacked uninsured motorist coverage mean?
Stacking combines UM or UIM limits across vehicles or policies. In Pennsylvania, for example, stacked coverage multiplies your limit by the number of vehicles on the policy unless you reject it in writing.
Does uninsured motorist coverage pay for my car?
UM bodily injury doesn't. UM property damage, where available, can pay for damage caused by an identified uninsured driver. Collision covers your car regardless of fault.
Related guides
- Minimum Car Insurance Requirements: What "30/60/25" Means and Why It's Rarely Enough
- PIP vs. Medical Payments Coverage: How Your Car Insurance Pays for Injuries
- What Happens After a Car Accident: Claims, Rate Increases and When People Call a Lawyer
- Driving Without Insurance: Penalties, Lapses and What Happens After a Crash
- How to Read a Car Insurance Quote and Compare Offers Apples to Apples
How we estimate this
This guide explains general rules and practices. Insurance terms vary by state, insurer and policy — check your policy documents and your state insurance department for the rules that apply to you. For cost estimates, try our calculators. Read the full methodology.