Updated July 2026
What Is Uninsured and Underinsured Motorist Coverage Insurance?
Uninsured motorist coverage (UM) pays when an at-fault driver has no insurance. Underinsured motorist coverage (UIM) pays when the at-fault driver's liability limits are too low to cover your full damages. Both coverages step in after the at-fault party's insurance is exhausted or confirmed absent. Your own insurer pays the claim, up to your UM/UIM policy limits, minus what the other driver's carrier already paid.
- You're stopped at a red light. The driver behind you has no insurance and causes $18,000 in medical bills and $7,000 in vehicle damage. If you carry $50,000 UM bodily injury and $25,000 UM property damage, your insurer pays the full $25,000 for injuries and repairs after you file a UM claim. Without UM/UIM, you pay out of pocket or sue the uninsured driver, who likely has no assets.
- An at-fault driver with Maine's minimum $50,000 bodily injury limit hits you. Your medical bills total $90,000. Their insurer pays the $50,000 limit. If you carry $100,000 UIM, your insurer pays the remaining $40,000. Without UIM, you're responsible for the $40,000 gap unless you sue and collect, which is rare in practice.
- A driver sideswiped your parked car and fled. You have $10,000 in damage. If your UM property damage coverage includes hit-and-run, your insurer pays the claim minus your deductible. If your policy excludes hit-and-run or you declined UM property damage, you file under collision coverage or pay the repair yourself.
Who Needs Uninsured and Underinsured Motorist Coverage Insurance?
Carry UM/UIM if you live in a state with a high uninsured driver rate, if you drive frequently in areas where minimum liability limits are common, or if your health insurance has high deductibles or excludes auto accident injuries. It's also critical if you can't afford to cover a $20,000+ medical bill or vehicle repair out of pocket after an at-fault uninsured driver hits you.
Compare your health insurance out-of-pocket maximum to typical accident medical costs in your area. If your health plan caps costs at $3,000 and you have savings to cover vehicle damage, UM/UIM is optional. If your health deductible is $6,000 or higher, or you lack collision coverage, UM/UIM is worth the premium because your own insurer pays immediately without a lawsuit.
How Much Does Uninsured and Underinsured Motorist Coverage Insurance Cost?
UM/UIM typically adds $8–$18 per month to your premium, or roughly $95–$215 annually, depending on your limits and state.
- Your UM/UIM limits — higher limits cost more, but the per-dollar cost decreases as limits rise.
- State uninsured driver rate — states with more uninsured motorists see higher UM/UIM premiums due to claim frequency.
- Whether you stack coverage — stacking UM/UIM across multiple vehicles on one policy increases limits and premium.
- Your liability limits — many carriers tie UM/UIM pricing to your liability coverage tier.
- Claim history — prior UM claims can raise your rate at renewal, though less than at-fault claims.
- Deductible on UMPD — choosing a $250 or $500 deductible for uninsured motorist property damage lowers premium.