When another driver is legally responsible for a crash, recovery can be limited if that driver has no liability insurance or limits below the covered damages. Uninsured motorist (UM) and underinsured motorist (UIM) coverage may respond to that shortfall, but who qualifies as an insured, what losses count, and how benefits are calculated are controlled by state law and policy wording—not one national rule.
Key Takeaways
- Uninsured motorist coverage generally applies when the at-fault driver has no insurance at all, or cannot be identified, as in many hit-and-run cases.
- Underinsured motorist coverage generally applies when the at-fault driver has some insurance, but not enough to cover the policyholder’s damages.
- Some states require UM/UIM coverage outright; others require insurers to offer it while allowing the policyholder to reject it in writing.
- "Stacking" — combining UM/UIM limits across multiple vehicles or policies — is allowed in some states, restricted in others, and prohibited by statute elsewhere.
- Because these rules vary so widely and change over time, this article intentionally avoids presenting a single nationwide table; it uses a handful of statute-verified state examples instead.
What uninsured motorist coverage actually does
Uninsured motorist coverage may pay covered damages when a person who qualifies as an insured under the policy is injured by a driver with no applicable liability insurance. Depending on the policy and state, insured people may include the named insured, certain household members, and occupants of a covered vehicle. Many states and policies also address unidentified hit-and-run drivers, but physical-contact, reporting, corroboration, or notice conditions can differ.
Some states also offer a separate uninsured motorist property damage component, which pays for damage to the policyholder’s vehicle caused by an uninsured driver. This is not universal; several states limit UM coverage to bodily injury only, leaving property damage from an uninsured driver to be handled under the policyholder’s own collision coverage instead. Whether UM property damage is available, and at what limit, depends entirely on the policyholder’s own state and policy.
What underinsured motorist coverage actually does
Underinsured motorist coverage addresses a related situation in which the responsible driver has liability insurance, but the available liability payment does not fully compensate covered damages. A UIM benefit may be limited by the insured’s UIM limit, offsets or reductions, settlement-and-notice conditions, exhaustion requirements, and the calculation method allowed by state law and the policy.
Fictional example (for illustration only): “Jordan” has covered damages that exceed the responsible driver’s available liability payment and also carries UIM coverage. The UIM claim may be reviewed for an additional covered payment, but the arithmetic is not automatically “damages minus the other driver’s limit.” Different states and policies can use offsets, gap-style calculations, exhaustion rules, consent requirements, or other conditions. No amount is guaranteed by this example.
Whether UM/UIM is required — it depends on the state
State approaches do not fit neatly into only two categories. Common structures include:
- Required minimum coverage: state law requires at least a stated level that cannot be fully removed in the ordinary personal policy.
- Included or offered coverage with a written choice: coverage may be included or offered at specified limits but can be rejected, reduced, or changed through a compliant written selection.
- Other state-specific structures: bodily-injury and property-damage components, UIM calculations, rejection forms, renewals, and commercial-policy rules may be treated differently.
A few statute-verified examples illustrate how differently this plays out:
- Kansas requires UM/UIM coverage matching the policyholder’s bodily injury liability limits but allows the named insured to reject the coverage above the state’s minimum liability limit, in writing (K.S.A. 40-284).
- Nebraska requires UM and UIM coverage at $25,000 per person / $50,000 per accident as a floor, and requires insurers to offer higher limits — up to $100,000 per person / $300,000 per accident — if requested in writing (Neb. Rev. Stat. § 44-6408).
- Indiana requires insurers to make UM/UIM available at limits matching the policyholder’s bodily injury liability coverage, with a UIM floor of $50,000, and allows the named insured to reject UM, UIM, or both in writing; a rejection is binding on every other insured person under that policy (Ind. Code § 27-7-5-2).
- Virginia requires UM/UIM coverage equal to the policyholder’s liability limits unless the named insured rejects it in writing; as in Indiana, that rejection binds every other insured person under the same policy (Va. Code § 38.2-2206).
These four states are examples only, chosen because their current statutory language could be directly verified. They are not a complete list, and a reader in any other state should not assume their state follows the same rule as any of these four.
Important limitation
Whether UM/UIM is mandatory, optional, or waivable — and the exact dollar floor involved — is a matter of the reader’s own state law, which can change. Always confirm current requirements with your own state department of insurance rather than relying on any general description, including this one.
Stacking: why it matters and why it isn’t universal
UM/UIM stacking refers to combining UM/UIM limits across more than one vehicle, or more than one policy, to reach a higher total available amount after a claim. For example, a household insuring two vehicles, each carrying $50,000 in UM coverage, might in a stacking state be able to combine those limits into $100,000 of available UM coverage for a single accident. In a non-stacking state, the same household would generally be limited to the single highest applicable limit, regardless of how many vehicles are insured.
Whether stacking is available, and under what conditions, is decided entirely at the state level, and the rules are more varied than a simple yes/no:
- Some states permit stacking by default, but allow an insurer to include an anti-stacking clause in the policy language itself.
- Some states require a written waiver from the policyholder before stacking can be limited, and treat a missing or defective waiver as leaving stacked coverage in place.
- Some states prohibit stacking by statute outright, regardless of what the insurer or policyholder might prefer.
- Kansas’s statute is an example of an explicit anti-stacking rule: it caps total recoverable UM/UIM benefits at "the highest limits of any single applicable policy," regardless of the number of vehicles, policies, or premiums involved (K.S.A. 40-284(d)).
- Wisconsin’s stacking rules illustrate how much this area of law can change over time: the state’s statute has been substantially amended multiple times over roughly two decades, each time altering how stacking and UM/UIM reduction provisions work (Wis. Stat. § 632.32).
Because stacking rules are genuinely this variable — and because this batch’s research did not find a single reliable, fully verified nationwide count of which states allow it — this article does not present a complete stacking table. To determine whether stacking is available, review the current state statute or regulator guidance together with the policy’s anti-stacking language, selection forms, and declarations page.
Hit-and-run claims are not handled identically everywhere
Because an unidentified hit-and-run driver can’t be confirmed as "insured" or "uninsured" in the ordinary sense, states and policies use varying approaches to decide how a hit-and-run claim is processed — commonly folding it into UM bodily injury coverage, but sometimes requiring independent corroboration of the accident (such as a police report or physical contact with the vehicle) before the claim can proceed. The specific evidentiary requirements are both policy-specific and state-specific, so documentation matters. For guidance on what to gather immediately after any accident, see What Happens After Filing an Auto Insurance Claim and Documents Needed for an Insurance Claim.
How UM/UIM interacts with health insurance and liability claims
UM/UIM coverage is not a substitute for health insurance, and the two are not mutually exclusive. Health insurance may pay medical providers directly and more quickly, while a UM/UIM claim addresses the broader financial picture — potentially including lost wages and damages not covered by health insurance — and is typically resolved on a different timeline. Some policies and states apply an offset that reduces a UM/UIM payout by amounts already recovered elsewhere, such as from the at-fault driver’s liability coverage; whether and how that offset applies depends on the specific policy and state, and is not something this article can generalize.
Reviewing your declarations page for UM/UIM
To see what UM/UIM coverage you actually carry, check your declarations page for:
- Whether UM and UIM are listed as separate line items, or combined
- The dollar limits attached to each (often shown in the same per-person/per-accident format as liability limits)
- Whether a UM property damage limit is listed separately, if your state offers it
- Any stacking designation, if your policy or state uses one
If any of these are unclear, your insurer or agent can explain exactly what your specific policy provides.
Common misunderstandings
Misunderstanding: UM/UIM coverage is the same thing in every state, just with different dollar amounts.
More accurate: The dollar amounts differ, but so do the underlying rules — whether the coverage is mandatory, whether it can be rejected, whether property damage is included, and whether stacking is available. Two states with identical UM dollar limits can still handle a claim very differently.
Misunderstanding: If the at-fault driver has "some" insurance, underinsured motorist coverage never applies.
More accurate: UIM coverage exists precisely for cases where the at-fault driver has insurance, but not enough to cover the damages. Having some coverage does not disqualify a claim from potentially involving UIM.
Misunderstanding: A hit-and-run accident with no identified driver can never be covered.
More accurate: Many UM policies extend to hit-and-run and unidentified-driver accidents, though the specific documentation and evidentiary requirements vary and should be confirmed with your insurer.
FAQ
Do I need uninsured motorist coverage if I already have full health insurance?
Health insurance and UM/UIM coverage address different categories and may use different reimbursement, offset, or subrogation rules. Health insurance generally addresses eligible medical treatment, while a UM/UIM claim may include other legally recoverable covered damages. This article does not determine whether a particular person should select the coverage.
Can UM/UIM coverage be removed or changed without any documentation?
Rejection, reduction, renewal treatment, cancellation, and notice requirements are governed by state law and policy terms. Many states require a written selection or rejection, but there is no safe nationwide “never” rule. Review the current declarations page, renewal documents, and any signed coverage-selection forms; a state insurance department can explain the applicable requirement.
Does UM coverage pay for my car repairs after a hit-and-run?
That depends on whether your state and policy include a UM property damage component, and whether your policy instead handles vehicle damage from an unidentified driver under your collision coverage. Check your declarations page or ask your insurer directly.
Important limitations
This article explains general concepts in uninsured and underinsured motorist coverage using a small number of statute-verified state examples. It is not a comprehensive summary of all fifty states’ rules, is not personalized insurance or legal advice, and does not predict how any specific claim will be handled. UM/UIM statutes are amended periodically; always verify current requirements with your own state department of insurance and your insurer.
Official sources
- NAIC: What Does Auto Insurance Cover?
- Kansas Statute 40-284 (2026)
- Nebraska Revised Statute § 44-6408
- Indiana Department of Insurance: Property & Casualty Review Standards
- Virginia Code § 38.2-2206, 2026 update
- Wisconsin Statute § 632.32
Conclusion
UM/UIM coverage exists because liability insurance is only as good as the driver who’s required to carry it — and not every driver does. Because the specific rules genuinely vary by state, the most useful next step for any reader is checking their own declarations page and their own state department of insurance, rather than assuming a rule they read here applies everywhere. For how liability limits themselves are structured, including a few state examples, see How Auto Insurance Liability Limits Work.
