UIM in the auto insurance field stands for underinsured motorist bodily injury. Underinsured motorist can also be referred to as UNDUM as well by some in the insurance industry.
Underinsured motorist is bundled with uninsured motorist bodily injury coverage (UM) in some states and other state they are sold separately -- so we will explain both coverages to you.
UM covers you, the insured members of your household, and your passengers for bodily/personal injuries, damages or death caused by an at-fault uninsured or hit-and-run driver (if the policy allows for an unknown vehicle or phantom vehicle). If you're involved in an accident where the other driver is at fault but has no insurance, your uninsured motorist coverage will cover your medical expenses, up to the limit on your policy.
If the other driver involved in an accident is uninsured, this coverage pays up to the limit you purchase. The coverage limits refer to the maximum amount that will be paid per person, per incident, respectively.
UIM is similar but covers you, the insured members of your household and your passengers for injuries, damages or death caused by the negligence of a person with insufficient insurance, thus the person is found to be underinsured. If you have an accident with a person whose coverage cannot meet your damages, your policy will meet the difference-up to the limit of liability listed on your policy.
If the other driver involved in an accident is underinsured, this coverage typically pays any difference between what the other driver's insurance covers and what your bodily injury coverage will pay. The coverage limits refer to the maximum amount that will be paid per person, per incident, respectively. If the limits you purchase are lower than an accident's costs, you'll be responsible for paying the amounts over your limits, unless you're covered by health insurance.
There are other types of underinsured and uninsured auto insurance as well. There is underinsured motorist property damage (UNDPD) which covers when property damage is sustained by an insured and the negligent operator possesses insurance, but the limits of liability carried by the negligent driver are not sufficient to cover the damages.
Then there is uninsured motorist property damage (UMPD) which covers your auto when property damage is sustained by an insured and the negligent operator does not possess insurance.
State laws and the terms of an auto insurance policy may cause the actual coverages for UM, UIM, UNDPD and UMPD to differ so ask an insurance agent about these coverages specifically if you thinking about buying them as part of your car insurance policy. Once you have the policy you can read through the terms of it for more information on what your particular coverages are for unisured and underinsured Motorist.
For more information on the various types of car insurance coverages, visit our coverage definitions page and our auto insurance glossary. When you've decided which coverages you need, it will be time to purchase a policy.