what is underinsured motorist coverage uim 
underinsured motorist coverage is a type of auto insurance it protects you if you re in an accident caused by someone who doesn t have sufficient insurance of their own in general if the at fault driver s policy has a limit that s lower than the cost of the damage to your vehicle or your medical bills and you have uim coverage your insurance company will cover the remaining amount the definition of underinsured and how uim coverage works varies by state underinsured motorist coverage is required in some states and can be purchased as an endorsement on your car insurance policy in others 12underinsured motorist coverage is different from uninsured motorist coverage which covers cases in which the at fault driver has no insurance at all 