Updated July 2026
What Is Uninsured and Underinsured Motorist Coverage Insurance?
Uninsured motorist coverage (UM) and underinsured motorist coverage (UIM) are optional add-ons to your auto policy that step in when the driver who hits you doesn't have insurance or doesn't have enough. UM pays when the other driver has zero coverage; UIM pays when their liability limits are too low to cover your medical bills and vehicle damage. Both coverages draw from your own policy, not the at-fault driver's, so you file the claim with your own carrier. New Hampshire doesn't mandate UM/UIM, but carriers must offer it when you buy a policy.
- You're stopped at a red light and a driver with no insurance rear-ends you at 40 mph. You have $8,000 in medical bills and $6,500 in vehicle damage. The at-fault driver has no policy and no assets. Your uninsured motorist coverage pays the $8,000 in medical costs (up to your UM bodily injury limit) and the $6,500 in property damage (up to your UM property damage limit). Without UM/UIM, you pay out of pocket or sue a driver who can't pay.
- A driver with minimum liability coverage runs a stop sign and T-bones your car. You have $45,000 in medical bills and lost wages. The at-fault driver carries $25,000 in bodily injury liability—the legal minimum in their state. Their policy pays the $25,000 maximum. Your underinsured motorist coverage pays the remaining $20,000 (up to your UIM limit). Without UIM, you absorb the $20,000 gap or pursue the driver personally, which rarely recovers anything.
- A driver sideswipes you on I-93 and flees. You have dashcam footage and a witness who recorded the plate number, but police can't locate the driver. You have $12,000 in vehicle damage and $3,000 in medical costs. Your uninsured motorist coverage pays both, minus your deductible, because you have evidence the collision occurred and the other driver fled. If you have no proof the other vehicle existed, most carriers deny the claim.
Who Needs Uninsured and Underinsured Motorist Coverage Insurance?
UM/UIM makes sense if you live in New Hampshire and don't carry collision or comprehensive coverage, because it's your only protection against an uninsured driver who totals your car. It's also critical if you have high medical costs or dependents who rely on your income, since 13% of New Hampshire drivers are uninsured and you can't recover damages from someone with no assets. If you carry minimum liability limits yourself, UM/UIM is often the cheapest way to protect against catastrophic injury costs when the other driver is underinsured.
Buy UM/UIM if the cost of replacing your vehicle or covering your medical bills out of pocket would create financial hardship and you don't have collision coverage or a health plan with zero-cost accident coverage. Skip it if you carry full coverage with low deductibles and comprehensive health insurance that doesn't exclude auto accidents. The decision turns on whether you're willing to absorb the loss when an uninsured driver hits you, because New Hampshire won't force them to pay and most have no recoverable assets.
How Much Does Uninsured and Underinsured Motorist Coverage Insurance Cost?
Uninsured and underinsured motorist coverage typically adds $8 to $18 per month to your premium, or $96 to $216 annually, depending on your coverage limits and location.
- Coverage limits you select—higher UM/UIM limits cost more, but the gap between $25,000 and $100,000 in coverage is often under $5 per month.
- Your county's uninsured driver rate—areas with higher percentages of uninsured motorists see higher UM/UIM premiums because claim frequency is higher.
- Whether you stack coverage across multiple vehicles—stacking lets you combine UM/UIM limits from all cars on your policy, which doubles or triples your protection but raises the premium proportionally.
- Your own liability limits—carriers often cap UM/UIM at your liability limit, so if you carry $100,000 in liability, you can't buy $250,000 in UM/UIM.
- State requirements—New Hampshire doesn't mandate UM/UIM, so carriers price it as optional; states that require it bake the cost into every policy.