Underinsured Motorist Coverage: When It Pays and How Much

Say you get T-boned at an intersection. The other driver is at fault and has insurance, but their bodily injury limit caps out at $25,000. Your hospital bill runs $80,000. Where does the remaining $55,000 come from?

That gap is what underinsured motorist (UIM) coverage fills. About 14% of U.S. drivers carry no insurance at all [1], which is the gap uninsured motorist coverage handles. The Insurance Information Institute's state ranking shows the uninsured rate varying widely, from under 6% in Maine to roughly 28% in Mississippi [2]. But the larger group nationally is drivers who carry the legal minimum, and the math from a minimum-limits policy stops well short of what a serious accident actually costs. The National Association of Insurance Commissioners notes that roughly one in three drivers nationally is either uninsured or underinsured [3].

This guide walks through how UIM coverage actually works, the two state models that change what your UIM pays out, the requirement landscape across the U.S., how much UIM to carry, and the FAQs that real drivers keep asking. By the end, you will know whether your current UIM limits leave you exposed.

What Underinsured Motorist Coverage Is

Underinsured motorist (UIM) coverage is the part of your auto policy that pays for your injuries and, in some states, your property damage when the at-fault driver has insurance but their liability limits are too low to cover what they caused [4]. It is your protection against the other driver's inadequate policy.

UIM has two components, and not every state offers both:

1. UIM bodily injury (UIMBI) pays for your medical bills, lost wages, and pain and suffering when an underinsured at-fault driver hurts you or your passengers.
2. UIM property damage (UIMPD) pays for your vehicle repair or replacement when the at-fault driver's property damage limit cannot cover the damage they caused. Florida's statute on UM/UIM coverage applies only to bodily injury, so Florida drivers do not have a UIMPD option through this coverage [5]. A handful of other states also limit or exclude UIMPD.

The trigger is specific. UIM pays only after the at-fault driver's liability insurance has been exhausted or determined to be insufficient. If the at-fault driver has no insurance at all, you would be filing under uninsured motorist coverage instead.

UIM vs. UM: The Trigger Distinction

The two coverages sit next to each other on your policy but pay on different events. Confusing them is the most common mistake drivers make when their carrier denies an initial claim.

Question	Uninsured Motorist (UM)	Underinsured Motorist (UIM)
When does it apply?	At-fault driver has no insurance	At-fault driver has insurance, but limits are too low
Hit-and-run treatment	Yes, hit-and-run drivers count as uninsured	No, UIM requires an identified at-fault driver with a policy
Who pays first?	Your UM, after a brief claim window	At-fault driver's policy pays first, then UIM fills the gap
Property damage?	Available in most (not all) states	Available in fewer states; some bundle it with UM PD

Source: state DOI consumer guides cited throughout this article

The practical version: if the at-fault driver had any insurance, your carrier will route the claim through UIM, not UM. If your claim is denied as "not uninsured," check whether your policy includes UIM and confirm your state's eligibility rules.

The Two Ways UIM Math Works: Excess vs. Limits-to-Fault

The single biggest source of UIM sticker shock is that "I have $100,000 in UIM" does not mean "I can recover $100,000 from my own policy." Whether your UIM stacks on top of the at-fault driver's payout or gets reduced by it depends on your state. There are two models.

Excess (or add-on) UIM. Your full UIM limit sits on top of whatever the at-fault driver's insurer paid. Virginia's UIM statute pays "without any credit for the bodily injury and property damage coverage available for payment" by default, unless the insured signs an election to reduce [6].

Concretely, if you carry $100,000 UIM and the at-fault driver pays $30,000 in liability, your UIM can pay up to $100,000 more, for a total possible recovery of $130,000.

Limits-to-fault (or offset, or reduced-by) UIM. Your UIM limit is reduced by what the at-fault driver already paid. New Jersey takes this further: "You are only eligible to receive reimbursement of underinsured motorist benefits if your Underinsured Motorist Coverage limits are higher than the Liability Coverage limits of the other driver" [7].

Concretely, the same $100,000 UIM facing a $30,000 at-fault liability payment gives you up to $70,000 from your UIM. Total recovery still tops out at $100,000. If you and the at-fault driver both carry $50,000 in a state with the New Jersey-style rule, you get nothing from your own UIM.

Here is the parallel math. Say you have $100,000 in UIM, the at-fault driver pays $30,000 in BI, and your damages are $80,000:

• Excess state: $30,000 from at-fault plus up to $100,000 from your UIM. Your $80,000 damages are fully covered, with $50,000 of UIM still available.
• Limits-to-fault state: $30,000 from at-fault plus up to $70,000 from your UIM ($100,000 cap minus $30,000 already paid). Your $80,000 damages are fully covered, with $20,000 of UIM still available.

Now run the same math at $150,000 in damages. The excess state covers $130,000 of it. The limits-to-fault state caps your total at $100,000. Most drivers buying UIM never check which model their state uses, and it changes the math by tens of thousands of dollars on a serious claim.

State Requirements: Who Must, Who Must Offer, Who Lets You Walk Away

State rules fall into three buckets. The Connecticut General Assembly's 50-state minimum requirements report is a useful cross-state reference [8], but the specifics live in each state's DOI guide.

Required in every policy. About half of all U.S. states plus D.C. require UM (and often UIM) on every auto policy [4].

Illinois requires uninsured motorist bodily injury limits of at least $25,000 per person and $50,000 per accident [9].

New Jersey makes UM/UIM standard on its "Standard Policy" but excludes it entirely from the cheaper "Basic Policy," so drivers who buy the Basic Policy have no protection against an uninsured or underinsured driver [7].

Required to be offered. In the rest of the states, insurers must offer UM/UIM, and the driver must reject the coverage in writing to opt out. Texas requires insurers to offer uninsured motorist coverage on every auto policy and to obtain a written rejection if a driver declines [10]. California works the same way, with a signed waiver as the only way to opt out [11]. Florida goes further: its rejection form must be on a state-approved document with a heading in 12-point bold type warning the driver about the coverage they are giving up [5].

Outlier rules to know. Florida has no UIMPD under its UM/UIM statute, only UIMBI [5]. New Jersey's Basic Policy strips out UM/UIM entirely [7]. Several states cap UMPD with a deductible: Illinois law requires the coverage be offered with a maximum $250 deductible [9]. Reddit threads regularly surface drivers who waived UMBI in one state and were surprised to learn they had also waived UMPD by default.

You can check the state requirements data page for the minimum liability and UM/UIM rules in every state, or compare the average premiums by state to see how your state stacks up. Always verify against your state's DOI consumer page before adjusting limits.

How Much UIM to Carry

There is a simple, defensible rule: your UIM bodily injury limits should mirror your bodily injury liability limits, with a floor at 100/300 (which is shorthand for $100,000 per person and $300,000 per accident).

Two reasons. First, in many states your UIM cannot legally exceed your own liability limit, so paying for higher UIM than you carry in liability is wasted premium. The New Jersey rule above is the strictest version of this; other states follow similar logic [7]. Second, the Treasury Federal Insurance Office calculated the average bodily injury liability claim severity at $24,211 in 2022 [1]. That figure is the average, so half of all serious BI claims run higher. A 25/50 UIM ceiling covers the average, but a moderate hospitalization with surgery and rehab sails past it.

If you carry significant assets, depend on your income, or live in a high-cost state where serious medical bills routinely cross six figures, push the floor to 250/500. The premium difference between 100/300 and 250/500 UIM is usually smaller than the premium difference between minimum and standard liability, because UIM is a relatively cheap add-on per dollar of coverage.

If you are not sure what UIM you currently carry, your declarations page is the source of truth. You can also see the full breakdown of how much auto insurance you actually need to anchor your decision.

When UIM Actually Pays

Two scenarios show the realistic dollar math.

Hospital scenario (UIMBI). Imagine you are hit by an at-fault driver carrying $25,000 in bodily injury liability, your state minimum. Your hospital bill, surgery, and rehab total $80,000. You carry $100,000 UIMBI. In an excess state, you collect $25,000 from the at-fault driver plus up to $100,000 from your UIM. In a limits-to-fault state, you collect $25,000 from at-fault plus $75,000 from your UIM ($100,000 cap minus $25,000 already paid). Either way, your $80,000 in damages is fully covered, and you still have room left for lost wages and pain and suffering, which UIM also covers.

Totaled car scenario (UIMPD). A driver pulls out and totals your $35,000 vehicle. Their property damage liability maxes at $25,000. If your state offers UIMPD and you carry it, the coverage fills the $10,000 gap. If your state does not offer UIMPD, or you waived it, your collision coverage pays after your deductible, and your insurer typically pursues subrogation against the at-fault driver to recoup what it can.

UIM covers more than medical bills. It also pays lost wages, replacement services if you cannot work, and pain and suffering damages [4]. Your passengers are typically covered too, which is the answer to one of the most common reader questions in the next section.

Why Health Insurance Isn't a Substitute

The most common objection to buying UIM is "I have good health insurance, why do I need it?" Three reasons.

First, health insurance covers medical bills only. UIM covers medical bills plus lost wages, pain and suffering, and damages your passengers suffer. Your passengers are usually not on your health plan.

Second, many health policies refuse to pay or pay reduced amounts when a third party caused the injury, on the theory that the at-fault driver's liability insurer (and your UIM as a backstop) should pay first. Personal injury attorneys on Reddit confirm this happens regularly in litigation.

Third, subrogation can force the issue. Even when your health insurer does pay your medical bills, it can require you to file a UIM claim so it can recover what it paid from your auto policy. You may not have a choice about pursuing the UIM claim once your health insurer learns a negligent driver caused the loss. If you carry strong health coverage but no UIM, your health insurer's recovery rights still bring you back to the auto policy, just without the lost-wages and pain-and-suffering protection you would have had.

Frequently Asked Questions

Is underinsured motorist coverage worth it if I have health insurance?

Usually yes. Health insurance covers medical bills, but UIM also pays lost wages, pain and suffering, and damages to passengers who may not be on your health plan. Health insurers can also subrogate, requiring you to recover from UIM so they can be reimbursed, which means a UIM claim is often unavoidable anyway.

How much can I get from an underinsured motorist claim?

It depends on your state's UIM model. In an excess state, your full UIM limit pays on top of whatever the at-fault driver's liability paid. In a limits-to-fault (or offset) state, your UIM limit is reduced by what the at-fault driver already paid. A $100,000 UIM policy facing a $30,000 at-fault payment gives you total recovery of $130,000 in an excess state and $100,000 in an offset state ($30,000 from at-fault plus $70,000 from your UIM).

Is UM/UIM coverage worth it?

For most drivers, yes. About 14% of U.S. drivers carry no insurance [1], and roughly one in three are either uninsured or underinsured [3]. State minimum bodily injury limits in many states top out at $25,000, while the average bodily injury claim in 2022 was $24,211 [1]. Carrying state-minimum coverage with no UM/UIM puts you one above-average claim away from paying out of pocket.

Does underinsured motorist coverage cover passengers?

Yes, in most states UIM bodily injury covers passengers in your vehicle who are injured by an underinsured at-fault driver. This is one of the strongest arguments for UIM if you regularly carry family members, friends, or rideshare passengers. Your health insurance only covers you, not them.

Can I add UIM coverage mid-policy?

Yes. Most carriers let you add or change UM/UIM mid-term, and the premium gets prorated for the remaining policy period. If you just had a close call or a near-miss with an underinsured driver, you do not have to wait until renewal to close the gap.

The Bottom Line

Underinsured motorist coverage pays when the at-fault driver has insurance, but their limits cannot cover what they caused. State-minimum liability is often $25,000 to $50,000 in bodily injury, and the average bodily injury claim in 2022 was $24,211 [1]. UIM is the gap-filler between what the at-fault driver carries and what you actually need.

Three steps to take this week:

1. Pull your declarations page and write down your current UIM limits.
2. Compare those limits to your bodily injury liability limits. If your UIM is lower, that is the gap to fix. Aim to at least match your liability limits, with a 100/300 floor.
3. Get comparison quotes that include UIM at matched limits. The cost difference between low and properly matched UIM is usually small per dollar of coverage, and you cannot know your number without comparing.

Compare rates from top carriers in about two minutes at quotefii.com.

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