6.4 Part C Uninsured/Underinsured Motorists
Key Takeaways
- Part C pays the insured for bodily injury (and in some states property damage) caused by an at-fault uninsured motorist (UM) or underinsured motorist (UIM); the insured must be legally entitled to recover from the other driver.
- An uninsured motor vehicle includes a vehicle with no liability insurance, an insolvent insurer, and a hit-and-run (phantom) vehicle that causes injury without physical contact in many states.
- Underinsured Motorists coverage applies when the at-fault driver has liability limits lower than the insured's damages; states use either a difference-in-limits or an excess (add-on) approach to calculate the payable amount.
- Stacking allows an insured to combine UM/UIM limits across multiple vehicles or policies where state law permits; anti-stacking clauses limit recovery to one vehicle's limit.
- Part C is first-party and reduced by amounts the insured recovers from the at-fault party; it does not pay for the insured's own at-fault conduct.
What Part C Covers
Part C - Uninsured Motorists Coverage is a first-party coverage that protects the insured when an at-fault driver cannot pay. It pays compensatory damages the insured is legally entitled to recover from the owner or operator of an uninsured motor vehicle because of bodily injury. Many states extend the coverage to include Underinsured Motorists (UIM) protection, and some allow an optional Uninsured Motorists Property Damage (UMPD) component.
The phrase "legally entitled to recover" is the trigger: the other driver must be at fault. If the insured caused the accident, Part C does not respond - it is not a substitute for the insured's own liability.
What Counts as an Uninsured Motor Vehicle
An uninsured motor vehicle (UM) includes:
| Type | Description |
|---|---|
| No insurance | A vehicle with no liability bond or policy in effect |
| Insolvent insurer | A vehicle whose liability insurer becomes insolvent |
| Denied claim | An insurer that denies coverage |
| Hit-and-run (phantom) | A vehicle that flees and cannot be identified |
Many states cover a hit-and-run even with no physical contact (a "phantom vehicle" that forces the insured off the road), though some require contact or independent corroborating evidence.
Trap: A vehicle owned by a government agency, or one already insured under the policy's own liability, is not an uninsured motor vehicle. UM responds to the other driver's lack of coverage, not the insured's.
Underinsured Motorists - the Two Methods
Underinsured Motorists (UIM) applies when the at-fault driver has liability insurance but not enough to cover the insured's damages. States compute the payable UIM amount two ways:
- Difference-in-limits (limits-based): UIM pays the difference between the insured's UIM limit and the at-fault driver's liability limit.
- Excess / add-on (damages-based): UIM pays the difference between the insured's actual damages and what the at-fault driver paid, up to the UIM limit.
Worked example - difference-in-limits: The insured carries $100,000 UIM; the at-fault driver carries $25,000 liability and pays it in full. Damages are $90,000. Under the difference-in-limits method, UIM pays $100,000 - $25,000 = $75,000, but only up to actual damages, so it pays $65,000 ($90,000 damages minus the $25,000 already received).
UIM Excess-Method Example and Offsets
Worked example - excess/add-on: Same facts: $100,000 UIM, at-fault driver pays $25,000, damages $90,000. The excess method pays damages minus the recovery, capped at the UIM limit: $90,000 - $25,000 = $65,000 (within the $100,000 limit). In this scenario both methods reach $65,000, but they diverge when damages exceed the UIM limit - the difference-in-limits method is then capped lower.
Part C is generally reduced by sums the insured recovers from the at-fault party, so the insured cannot collect the same dollars twice. The insurer also gains subrogation rights against the uninsured or underinsured driver after paying.
Stacking and Anti-Stacking
Stacking lets an insured combine UM/UIM limits where state law allows:
- Intra-policy (vertical) stacking: combine limits across multiple vehicles on one policy.
- Inter-policy (horizontal) stacking: combine limits across separate policies.
Worked example - stacking: An insured covers three vehicles on one policy, each with $50,000 UM. In a state permitting intra-policy stacking, the insured may access 3 x $50,000 = $150,000 of UM coverage for one injury. In an anti-stacking state, recovery is limited to a single $50,000 limit regardless of how many vehicles are insured.
Many insurers include anti-stacking clauses, and many states enforce them; others mandate stacking or require the insurer to offer it. The exam tests the concept, not any one state's rule.
Limits, Rejection, and Why Part C Matters
UM/UIM is mandatory in many states and must be offered in others, usually at limits equal to the insured's liability limits unless the insured rejects higher UM in writing. Because roughly one in seven U.S. drivers is uninsured (Insurance Research Council estimates), Part C is the coverage that protects responsible insureds from irresponsible ones.
Trap: Part C pays for bodily injury by default; property damage to the insured's vehicle from an uninsured driver is usually handled through Collision under Part D (subject to the deductible) or, in states offering it, the optional UMPD component. Do not assume UM automatically repairs the insured's car.
An insured carries $100,000 Underinsured Motorists coverage. The at-fault driver has $30,000 liability limits, pays them in full, and the insured's total damages are $110,000. Under the difference-in-limits (limits-based) method, what is the maximum UIM payment?
In a state that permits intra-policy stacking, an insured has three autos on one policy each with $50,000 Uninsured Motorists coverage. What is the maximum UM available for a single injury?
UM vs. UIM and the Stacking Concept
Part C protects the insured when the other driver is at fault but uninsured or underinsured. The exam tests the precise distinction.
| Coverage | Responds when the at-fault driver |
|---|---|
| Uninsured Motorist (UM) | Has no liability insurance (or is a hit-and-run) |
| Underinsured Motorist (UIM) | Has insurance, but limits too low to cover the damages |
| UM Property Damage | (Where offered) damages the insured's vehicle - else use collision |
Worked UIM example: an insured suffers $80,000 in injuries. The at-fault driver carries only $25,000 in liability. With $100,000 UIM, the insured collects $25,000 from the other driver and the UIM pays the $55,000 gap (limit $100,000 minus the $25,000 already paid, capped at actual damages).
Exam Trap: Stacking lets an insured combine UM/UIM limits across multiple vehicles or policies (where state law allows), so two cars each with $50,000 UM can yield $100,000. Many states permit insurers to include an anti-stacking clause, and UM/UIM limits generally cannot exceed the policy's liability limit unless higher limits are specifically purchased.