Underinsured motorists (UIM) coverage applies to bodily injury and, in some states, property damage incurred by an insured when an auto accident is caused by a motorist who is not sufficiently insured.
Depending on the jurisdiction, UIM coverage may be written with a limits trigger or a damages trigger. With a limits trigger, UIM coverage applies when the limits of liability carried by the other motorist are lower than the UIM limits carried by the insured. With a damages trigger, UIM coverage applies when the insured's damages are more than the at-fault party's available limits.