Uninsured & Underinsured Motorist Coverage: Complete Guide 2026

Imagine you're driving home from work on a clear afternoon when another driver runs a red light and slams into your vehicle. You suffer injuries, your car is totaled, and then you discover the other driver has no insurance at all. Without the right coverage, you could be left paying tens of thousands of dollars out of pocket. This is exactly the scenario that uninsured motorist (UM) and underinsured motorist (UIM) coverage is designed to protect against.

What Is Uninsured Motorist Coverage?

Uninsured motorist coverage (UM) is a type of car insurance that pays for your injuries and property damage when you're hit by a driver who has no auto insurance at all. According to the Insurance Research Council, approximately 13% of drivers in the United States were uninsured in 2025, meaning roughly 1 in 8 drivers on the road could leave you high and dry after an accident. In some states, that number climbs above 20%.

UM coverage typically has two components:

• UM Bodily Injury (UMBI) — Covers medical expenses, lost wages, and pain and suffering for you and your passengers when an uninsured driver causes an accident.
• UM Property Damage (UMPD) — Covers damage to your vehicle caused by an uninsured driver. In some states, this also covers hit-and-run accidents.

What Is Underinsured Motorist Coverage?

Underinsured motorist coverage (UIM) kicks in when the at-fault driver has insurance, but their coverage limits are too low to fully pay for your damages. For example, many states require only the minimum liability coverage — which might be $25,000 per person for bodily injury. If your medical bills total $80,000, the other driver's insurance would pay only $25,000, leaving you to cover the remaining $55,000 unless you have UIM coverage.

UIM works on the same principle as UM: it supplements the at-fault driver's insufficient coverage up to the limits of your own UIM policy. The key is that your UIM limits should ideally be set higher than the average driver's liability limits in your state, giving you a meaningful safety buffer.

State-by-State: Which States Require UM/UIM?

UM and UIM requirements vary dramatically by state. Some states require drivers to carry UM/UIM as part of their mandatory auto insurance, while others make it optional. Here's a breakdown:

How UM/UIM Coverage Works in Practice

Let's walk through a real-world scenario to illustrate how UM and UIM work:

However, if your UIM limit is only $25,000, you would receive the full $25,000 from your UIM policy but still be responsible for $45,000 in remaining expenses. This is why financial advisors generally recommend setting UIM limits at least equal to your own liability limits, if not higher.

Hit-and-Run Accidents: Does UM Cover Them?

Hit-and-run accidents are one of the most common uses of uninsured motorist property damage (UMPD) coverage. When a driver flees the scene and cannot be identified, traditional liability claims are impossible. In this situation:

• UMPD coverage pays for repairs to your vehicle (subject to your deductible)
• UMBI covers your medical injuries if you can identify the at-fault driver
• In states with "phantom vehicle" UMPD coverage, you may be covered even when the driver is never found

Many insurers now offer UMPD with a deductible as low as $250-$500, making it an affordable addition to any policy. Given the rising number of hit-and-run incidents across the US — with over 737,000 reported in 2024 alone — this coverage has become increasingly valuable.

How Much UM/UIM Coverage Do You Need?

While state minimums exist for liability coverage, there are no federal mandates for UM/UIM. Financial experts recommend following these guidelines:

Stacked vs. Unstacked UM/UIM Coverage

If you have multiple vehicles on your policy, you may have the option to "stack" your UM/UIM coverage. Stacking means you can combine the coverage limits from all your vehicles to increase the total amount available after an accident.

• Unstacked: Coverage is limited to the per-vehicle limit shown on your policy
• Stacked: You can multiply your per-vehicle limit by the number of vehicles insured, significantly increasing your protection

For example, if you have three vehicles each with $100,000/$300,000 in UMBI limits, stacked UMBI would give you $300,000 per person / $900,000 per accident. Stacking adds a modest premium cost — typically 20-40% more per vehicle — but can provide substantial additional protection for families with multiple drivers.

How to Add UM/UIM to Your Policy

Adding UM and UIM coverage is typically straightforward. Contact your insurance company or agent and request a quote. Your insurer will need:

• Your current policy number
• The coverage limits you'd like to add
• Designation of whether you want stacked or unstacked coverage

The cost of UM/UIM coverage varies by state, driver profile, and claims history, but most drivers pay between $50 and $200 per year for comprehensive UM/UIM protection — a relatively small price compared to the potential financial devastation of being uninsured on the road.

Key Takeaways

• About 13% of US drivers are uninsured, making UM coverage essential in most states
• UIM protects you when the at-fault driver's liability limits are too low to cover your damages
• Many states offer stacked UM/UIM options for multi-vehicle households
• UMPD specifically covers hit-and-run accidents, which are increasingly common
• The cost of UM/UIM is typically $50-$200/year — a strong return on investment