What Is Uninsured/Underinsured Motorist Coverage?

You can do everything right with your own car insurance and still be left paying out of pocket after an accident that wasn’t your fault. That happens when the at-fault driver has no insurance or not enough to cover your damages. Uninsured and underinsured motorist coverage exists to fill exactly this gap, protecting you and your passengers when the other driver can’t.

This guide explains what uninsured and underinsured motorist coverage is, how UM and UIM differ, the bodily injury and property damage components, why this coverage matters given how many drivers are uninsured, and how to set your limits. Understanding this often-overlooked coverage helps you avoid a costly gap when you need protection most.

What This Coverage Does

Uninsured and underinsured motorist coverage protects you financially when you’re in an accident caused by a driver who either has no insurance or doesn’t have enough to cover your damages. Normally the at-fault driver’s insurance would pay for your medical bills, lost wages, and other costs, but if they lack coverage, there’s nothing on their side to pay.

That’s where this coverage steps in, paying for those costs so you’re not left covering them yourself. Without it, you could be forced to pay out of pocket for medical bills or vehicle repairs from an accident that wasn’t your fault. It can even protect you if you’re hit as a pedestrian by an uninsured driver.

UM vs. UIM: The Difference

Though often bundled together, uninsured and underinsured motorist coverage address two different situations. Understanding the distinction helps you see why carrying both matters.

With UIM, the at-fault driver’s policy pays up to its limit first, and then your underinsured motorist coverage kicks in to cover the rest, up to your limits. Many insurers bundle UM and UIM together so you don’t accidentally miss one. Both work similarly once triggered, paying the costs the at-fault driver can’t.

The Bodily Injury Component (UMBI/UIMBI)

Like liability coverage, uninsured and underinsured motorist coverage breaks into bodily injury and property damage. The bodily injury portion, UMBI or UIMBI, covers you and your passengers for medical expenses, lost wages, and sometimes pain and suffering after an accident caused by an uninsured or underinsured driver.

This coverage is particularly valuable because it can offer higher limits than medical payments or personal injury protection, and you don’t have to worry about copays or coinsurance the way you might with health insurance. If a driver with no insurance injures you and your passengers, UMBI can step in to cover the medical bills.

The Property Damage Component (UMPD/UIMPD)

The property damage portion, UMPD or UIMPD, covers damage to your vehicle when it’s hit by an uninsured or underinsured driver. If an uninsured driver damages your car, UMPD pays for the repairs up to your policy limit. In some states this coverage applies to hit-and-run accidents as well.

Not all states offer UMPD, and where it’s available it may carry a deductible and have coverage limits that vary by state. Because availability and rules differ, it’s worth asking your insurer whether UMPD makes sense for you and how it interacts with collision coverage, which can also pay for your vehicle damage. Use our car insurance calculator to estimate the cost of adding UM/UIM.

Why This Coverage Matters

Driving without insurance is more common than many people realize, and you never know when you might have an accident with an uninsured driver. In some states, more than one in five drivers carries no insurance, making the risk of being hit by an uninsured motorist real and significant.

If you live in a state with a high percentage of uninsured drivers, this coverage is especially valuable. The cost of adding it is usually small compared to the potential financial impact of an accident with an uninsured or underinsured driver. For a modest premium increase, you gain protection against a scenario entirely outside your control.

How Much Should You Carry?

Experts generally recommend matching your uninsured/underinsured motorist limits to your liability limits. If you carry 100/300 in liability coverage, carrying 100/300 in UM/UIM ensures balanced protection whether you cause an accident or are hit by an uninsured driver. Standard UMBI limits are listed per person and per accident, like liability.

In some states with multiple vehicles on a policy, you may be able to stack your UM/UIM coverage, multiplying your available limits across vehicles. Stacking isn’t available everywhere or from every insurer, but where allowed it can meaningfully increase your protection. Our guide to how much car insurance you need covers setting limits in depth.

Is It Required?

Whether you must carry uninsured/underinsured motorist coverage depends on your state. Not all states require it, but many mandate at least one form. In some states, insurers must offer it and you can reject it in writing, though signing that waiver without understanding the risk can leave you exposed.

Even where it’s optional, most experts advise against skipping it, since the cost is usually small relative to the protection. Before declining UM/UIM, consider how you’d pay your medical bills and repair costs if an uninsured driver hit you. Our state requirement guides note which states mandate this coverage.

Frequently Asked Questions

What is uninsured motorist coverage?

Uninsured motorist coverage protects you and your passengers when you’re in an accident caused by a driver with no insurance. It pays for costs like medical bills, lost wages, and sometimes vehicle damage that the at-fault driver can’t cover, so you don’t pay out of pocket.

What’s the difference between UM and UIM?

Uninsured motorist (UM) coverage applies when the at-fault driver has no insurance at all. Underinsured motorist (UIM) coverage applies when they have insurance but not enough to cover your damages. With UIM, their policy pays first, then yours covers the rest up to your limits.

What’s the difference between UMBI and UMPD?

UMBI (bodily injury) covers medical expenses, lost wages, and sometimes pain and suffering for you and your passengers. UMPD (property damage) covers repairs to your vehicle. Not all states offer UMPD, and where available it may carry a deductible.

Is uninsured motorist coverage required?

It depends on your state. Not all states require it, but many mandate at least one form. In some states, insurers must offer it and you can reject it in writing. Even where optional, most experts recommend carrying it.

How much UM/UIM coverage should I have?

Experts recommend matching your UM/UIM limits to your liability limits for balanced protection. If you carry 100/300 liability, carrying 100/300 UM/UIM ensures you’re equally protected whether you cause an accident or are hit by an uninsured driver.

Does UM coverage apply to hit-and-runs?

In many states, uninsured motorist coverage applies to hit-and-run accidents, since the at-fault driver effectively has no available insurance. Rules vary by state, so confirm with your insurer whether your UM coverage includes hit-and-run protection.

What is stacking UM/UIM coverage?

In some states, if you have multiple vehicles on a policy, you can stack your UM/UIM coverage, multiplying your available limits across vehicles. For example, two cars each with 100/300 could stack to 200/600. Stacking isn’t available everywhere or from every insurer.

Is UM/UIM worth the cost?

For most drivers, yes. The cost of adding UM/UIM is usually small compared to the potential financial impact of an accident with an uninsured or underinsured driver. Given how common uninsured drivers are, it provides valuable protection for a modest premium.

The Bottom Line

Uninsured and underinsured motorist coverage protects you when an at-fault driver can’t, whether because they have no insurance or not enough. UM applies when the other driver is uninsured, while UIM covers the gap when their coverage falls short. Both break into bodily injury and property damage components.

This coverage matters because uninsured driving is common, and being hit by an uninsured motorist is a real risk entirely outside your control. The bodily injury portion covers you and your passengers’ medical costs and lost wages, while the property damage portion, where available, covers your vehicle. For a modest premium, you close a significant gap.

Experts recommend matching your UM/UIM limits to your liability limits for balanced protection, and stacking can increase coverage where allowed. Whether required or optional in your state, this coverage is one most drivers shouldn’t skip. Before declining it, consider how you’d handle the costs of an accident an uninsured driver caused.

Ready to make sure you’re protected against uninsured drivers? Visit Matrix Insurance to explore your options. Use our car insurance calculator to estimate the cost of UM/UIM coverage, or contact our team for personalized guidance on setting your limits.