Quick Answer: Uninsured Motorist (UM) and Underinsured Motorist (UIM) coverage protect you, your resident family members, and your passengers when an at-fault driver causes a crash but carries either zero auto liability insurance (or flees in a hit-and-run) or state-minimum liability limits too low to pay your full hospital bills, lost wages, and vehicle repairs. According to the Insurance Research Council (IRC), approximately 1 in 7 U.S. drivers (over 14% nationally) drives completely uninsured—and tens of millions more carry only $15,000 to $25,000 in state-minimum coverage.
While state laws force you to buy Bodily Injury and Property Damage Liability to protect other people when you make a mistake, UM/UIM is the coverage that protects your own household from everyone else on the road. In this guide—part of our types of auto insurance coverage explained cluster—we break down UMBI, UIMBI, and UMPD, explain how “stacked vs. unstacked” coverage works, and show why matching your UM/UIM limits to your liability limits is one of the smartest values in personal finance.
The 4 Components of Uninsured & Underinsured Motorist Coverage
Depending on your state’s insurance statutes—which you can verify through the NAIC Consumer Auto Insurance guide—UM/UIM is divided into four distinct sub-coverages on your policy declarations page:
| Coverage Type | When It Triggers | What It Pays For | Typical Deductible |
|---|---|---|---|
| 1. Uninsured Motorist Bodily Injury (UMBI) | At-fault driver has no active policy, a lapsed policy, a stolen car, or flees in an unidentified hit-and-run. | Medical bills, surgery/rehab, lost income, permanent disability, and pain & suffering for you and your passengers. | $0 deductible |
| 2. Underinsured Motorist Bodily Injury (UIMBI) | At-fault driver has insurance, but their bodily injury limit (e.g., $25,000) is exhausted before your $90,000 hospital & wage loss is paid. | Bridges the gap between the at-fault driver’s liability limit and your own UIMBI policy limit. | $0 deductible |
| 3. Uninsured Motorist Property Damage (UMPD) | An uninsured driver damages your vehicle or property (available in ~30 states; some states require identifying the driver). | Repairs to your car or Actual Cash Value replacement up to the state UMPD limit ($3,500–$100,000+). | $0–$300 state-set deductible (often lower than Collision) |
| 4. Underinsured Motorist Property Damage (UIMPD) | At-fault driver carries state-minimum Property Damage Liability (e.g., $5,000–$10,000) and totals your $38,000 SUV. | Covers the remaining damage to your vehicle (if you don’t use your own collision coverage). | Varies by state |
Real-World Claim Math: How UIM Saves You From State-Minimum Drivers
Many drivers assume that as long as the person who hits them has an insurance card, the other driver’s policy will pay for everything. Look at what actually happens in a serious intersection T-bone crash when the at-fault driver carries a standard $25,000/$50,000/$25,000 state-minimum policy:
- Your Total Losses: Emergency room trauma care, orthopedic surgery, 8 weeks of physical therapy, and 6 weeks of missed paychecks total $85,000.
- What the At-Fault Driver’s Insurer Pays: Their policy caps out at their $25,000 per-person Bodily Injury limit. Once their insurer writes a $25,000 check, their legal obligation ends—leaving a $60,000 unpaid gap.
- How Your Underinsured Motorist (UIM) Coverage Steps In: If you carry $100,000/$300,000 UIM coverage on your own policy, your insurer pays the remaining $60,000 directly to you (up to the $75,000 net difference between their $25k limit and your $100k limit). Without UIM, you would have to sue an underinsured driver who likely has no attachable personal assets.
Why UM/UIM Is Still Valuable Even If You Have Good Health Insurance
A common misconception is that employer health insurance makes Uninsured Motorist Bodily Injury redundant. In reality, UMBI/UIMBI covers four critical financial exposures that health insurance never touches:
- 1. Lost Wages & Reduced Earning Capacity: Health insurance pays doctors and hospitals, not your mortgage or lost paycheck while you recover from a fracture or concussion. UM/UIM reimburses lost income.
- 2. High Health Insurance Deductibles & Out-of-Pocket Maximums: Many family health plans carry $3,000 to $8,000 annual deductibles and 20% coinsurance. UMBI has a $0 deductible.
- 3. Passengers in Your Vehicle Whoaren’t on Your Health Plan: If you are driving friends, carpooling coworkers, or extended family, your health insurance does not cover them—your UM/UIM policy covers every passenger in your car.
- 4. Pain, Suffering, Scarring & Long-Term Disability: UM/UIM stands in the shoes of the at-fault driver’s liability policy, meaning it compensates non-economic damages as well as medical bills.
- 5. Pedestrian & Bicyclist Protection: In most states, your auto policy’s UM/UIM coverage follows you and your resident family members even when you are walking in a crosswalk, jogging, or riding a bicycle and get struck by an uninsured or hit-and-run driver!
Stacked vs. Unstacked Uninsured Motorist Coverage Explained
In roughly 30 states (including Florida, Pennsylvania, and several Midwest and East Coast states), multi-car households can choose between Unstacked and Stacked UM/UIM coverage:
- Unstacked UM/UIM: Your stated policy limit (for example, $100,000 per person / $300,000 per accident) is the maximum available for any single crash, regardless of how many vehicles you insure.
- Stacked UM/UIM: Your per-person and per-accident limits are multiplied by the number of vehicles on your policy. For example, if you insure 2 cars with $100,000/$300,000 Stacked UM/UIM, your effective protection doubles to $200,000 per person / $600,000 per accident across any crash.
To see how adding or stacking UM/UIM affects your total 6-month rate, test different coverage tiers on our Auto Insurance Premium Calculator and review our breakdown of what factors determine your insurance premium.
Economic vs. Non-Economic Damages Covered by UMBI and UIMBI
Unlike Medical Payments (MedPay) coverage—which only reimburses hospital and doctor invoices up to a small $1,000 to $10,000 cap—Uninsured and Underinsured Motorist Bodily Injury coverage steps into the legal shoes of the at-fault driver. That means you can recover both economic (out-of-pocket) and non-economic (quality-of-life) damages up to your policy limit:
- Emergency & Ongoing Medical Expenses: Ambulance transport, ER trauma care, diagnostic MRIs, surgery, hospital stays, physical therapy, chiropractic rehab, and future medical procedures.
- Lost Wages & Future Earning Capacity: W-2 wages, self-employment income, or freelance revenue lost while recovering, plus long-term disability reduction if injuries prevent you from returning to your career.
- Pain, Suffering & Mental Anguish: Compensation for chronic physical pain, disfigurement, surgical scars, PTSD, and loss of consortium/enjoyment of daily life.
- Wrongful Death & Funeral Expenses: Survivor benefits for family members if an uninsured or drunk hit-and-run driver causes a fatal accident.
Step-by-Step: How to Protect Your UM/UIM Claim Rights After a Crash
Because UM/UIM claims involve strict policy notice deadlines and subrogation rules, follow these five steps immediately after a hit-and-run or crash with a driver who admits they have no insurance or only state-minimum limits:
- Call 911 and Obtain an Official Police Crash Report: Almost every auto policy requires a formal police report filed within 24 hours to validate a hit-and-run Uninsured Motorist claim.
- Document Independent Witness Contact Info & Dashcam Video: In “phantom vehicle” crashes where a reckless driver forces you off the road without physical contact, many states require either physical contact or independent witness/dashcam corroboration to trigger UM coverage.
- Notify Your Own Insurer Immediately of a Potential UM/UIM Claim: Even when the crash is 100% the other driver’s fault, open a notice file with your own insurer so they can verify the other driver’s coverage status.
- Never Sign a General Liability Release With the At-Fault Insurer Without Your UIM Carrier’s Written Consent: Before accepting an underinsured driver’s $25,000 policy-limit check, your own UIM insurer must grant written consent to settle (or waive subrogation) so you don’t accidentally void your Underinsured Motorist coverage.
- Review Your Declarations Page for Multi-Car Stacking & Umbrella Options: Check whether your policy includes Stacked UM/UIM or if your personal umbrella policy includes an Excess UM/UIM endorsement.
Difference-in-Limits (Offset) States vs. Add-On (Excess) UIM States Explained
One of the most important state-by-state statutory differences in Underinsured Motorist (UIM) law is how your state calculates the payout when the at-fault driver’s liability limit is subtracted:
- Difference-in-Limits (Offset / Reduction) States: In an offset state, your UIM limit sets the maximum combined recovery from both policies together, and the at-fault driver’s liability payout is subtracted from your UIM limit. For example, if the at-fault driver carries $25,000 Bodily Injury Liability and you also carry $25,000 UIM in an offset state, you collect $0 from your UIM policy because $25,000 minus $25,000 equals zero! That is why carrying only state-minimum UIM in an offset state provides very little underinsured protection—you should carry at least $100,000/$300,000 so there is a substantial cushion above a state-minimum driver.
- Add-On (Excess) States: In an add-on state, your full UIM limit stacks on top of the at-fault driver’s liability limit whenever your verified damages exceed their policy cap. If you suffer $125,000 in medical and wage losses, the at-fault driver’s $25,000 limit pays first, and your $100,000 add-on UIM policy can pay the full remaining $100,000.
Frequently Asked Questions About Uninsured & Underinsured Motorist Coverage
Is Uninsured Motorist coverage required by state law?
Approximately 20 states and Washington, D.C. require drivers to carry Uninsured Motorist Bodily Injury (UMBI) by law, while most remaining states require insurance companies to include UM/UIM on every quote unless the policyholder signs a formal written rejection form. Even in states where it is optional, consumer advocates universally recommend keeping UM/UIM equal to your liability limits.
Do I need Uninsured Motorist Property Damage (UMPD) if I already have Collision coverage?
If you already carry Collision coverage, your collision policy will repair your car after a crash with an uninsured driver or hit-and-run driver regardless of whether you have UMPD. However, in many states UMPD carries a much lower deductible ($0 to $250) than a $500 or $1,000 collision deductible and adds only $2 to $5 per month to your premium.
Will filing an Uninsured Motorist claim raise my car insurance rates?
Because an Uninsured or Underinsured Motorist claim only applies when the other driver was legally at fault for the crash, state insurance regulations in most jurisdictions prohibit or strictly limit insurers from applying an at-fault surcharge for a not-at-fault UM/UIM claim.
