Updated July 2026
What Is Uninsured and Underinsured Motorist Coverage Insurance?
Uninsured motorist coverage (UM) and underinsured motorist coverage (UIM) protect you when another driver causes a crash but can't pay for the damage. UM pays when the at-fault driver has no insurance at all. UIM pays when their liability limits are too low to cover your medical bills, lost wages, and vehicle repair costs. Both coverages step in only after the at-fault driver's liability insurance is exhausted or confirmed absent.
- You're stopped at a red light in Boise. The driver behind you doesn't brake in time and rear-ends your car. You have $8,000 in medical bills and $5,500 in vehicle damage. The at-fault driver has no insurance. Your uninsured motorist coverage pays your medical bills up to your UM limit, and if your policy includes UM property damage, it covers the vehicle repair minus your deductible.
- A driver runs a stop sign in Idaho Falls and T-bones your car. You suffer a broken collarbone and miss six weeks of work. Your total damages — medical bills, lost wages, and pain and suffering — come to $42,000. The at-fault driver carries Idaho's minimum liability limit of $25,000 per person. Their insurer pays the $25,000 maximum. Your underinsured motorist coverage pays the remaining $17,000, up to your UIM policy limit.
- Your car is sideswiped in a parking lot in Coeur d'Alene. The other driver leaves the scene. You file a police report but the driver is never identified. Your uninsured motorist coverage treats this as an uninsured driver claim and pays for your injuries and, if your policy includes it, your vehicle damage up to your UM limits.
Who Needs Uninsured and Underinsured Motorist Coverage Insurance?
You should carry uninsured and underinsured motorist coverage if you live in an area with a high percentage of uninsured drivers, if you have significant medical expenses or income you'd lose during recovery, or if you can't afford to pay out-of-pocket for injuries caused by someone else. Idaho's 14% uninsured driver rate means roughly one in seven at-fault drivers won't have insurance to pay your claim.
Compare your health insurance deductible and out-of-pocket maximum to your potential injury costs in a serious crash. If your health plan leaves you with $5,000 to $10,000 in exposure and you don't have that in accessible savings, UM/UIM coverage is worth the $10 to $15 per month. If the at-fault driver's liability limit is $25,000 and your medical bills and lost income could exceed that in a moderate injury, UIM fills the gap your health insurance won't.
How Much Does Uninsured and Underinsured Motorist Coverage Insurance Cost?
Uninsured and underinsured motorist coverage typically adds $8 to $18 per month to an Idaho auto insurance policy, or roughly $95 to $215 annually, depending on your selected limits and whether you include property damage coverage.
- Your UM/UIM coverage limits — higher limits cost more, but protect you against drivers with severe injury claims.
- Whether you add UM property damage coverage — some Idaho policies exclude vehicle damage or cap it at $3,500, which lowers cost but leaves you exposed.
- Your county's uninsured driver rate — counties with higher percentages of uninsured drivers see slightly higher UM premiums.
- Stacking options if you insure multiple vehicles — stacked UM coverage combines limits across all vehicles on your policy, increasing both protection and cost.
- Your liability limits — carriers often tie UM/UIM limits to your liability coverage, so raising one affects pricing for both.