Your own auto policy contains the money that saves you when the other driver has none. Uninsured motorist coverage handles the driver with no policy at all, or the hit-and-run driver who is never found. Supplementary uninsured/underinsured motorist coverage handles the driver whose state-minimum policy runs out while your hospital bills keep climbing.
UM comes standard with every New York auto policy. SUM is elective, and most people select it without knowing they did. If your SUM limit sits at the state minimum, a serious injury caused by a minimally insured driver leaves you almost nowhere to turn.
Below: how both coverages work, the deadlines that apply, and the one choice you can make today that outweighs almost anything you can do after a crash.
The problem both coverages solve
New York requires drivers to carry bodily injury liability coverage of only $25,000 per person and $50,000 per accident. Those minimums have not moved in decades. One night in a trauma unit can pass $25,000. A spinal surgery can exceed $100,000. When the at-fault driver carries the minimum, his policy runs dry long before your losses do.
Many drivers carry nothing at all. Lapsed policies, suspended registrations, out-of-state cars, stolen vehicles, hit-and-run drivers who are never found. In those cases there is no liability policy to claim against.
Insurance Law § 3420 answers the first problem by requiring uninsured motorist protection in every New York auto policy. SUM coverage, governed by the same section and by Insurance Law § 3420(f)(2), answers the second. Together they let your own policy stand in for the coverage the other driver should have had.
UM: the mandatory floor
Every policy issued in New York includes uninsured motorist coverage at the statutory minimum of $25,000 per person and $50,000 per accident. It applies when the at-fault driver has no insurance, when the vehicle was stolen or unregistered, and in hit-and-run cases where the driver is never identified.
Two points matter for hit-and-run claims. First, there generally must be physical contact between the unidentified vehicle and you or your car. A driver who runs you off the road without touching you creates a harder claim. Second, report to the police promptly. Carriers scrutinize hit-and-run claims closely. A same-day police report anchors the file.
UM is only a floor. At $25,000 per person, it covers an uninsured driver no better than a minimally insured one. For serious injuries, SUM is the coverage that changes outcomes.
SUM: the coverage you choose, and usually choose wrong
SUM raises your protection above the floor and extends it to underinsured drivers. A driver is underinsured when his liability limit is lower than your SUM limit. Your own carrier then pays the difference, up to your SUM limit, minus what you collected from the other driver.
The mechanics are simple. Say you carry $250,000 in SUM and the at-fault driver carries the $25,000 minimum. You collect his $25,000, then claim up to $225,000 more from your own policy. Now say your SUM limit is $25,000, matching his. He is not underinsured relative to your policy. Your SUM coverage pays nothing. Same crash, same injuries, radically different recovery. A checkbox on the day you bought the policy decided it.
Since 2018, New York insurers must offer SUM at limits equal to your bodily injury liability limits. You must reject the higher amount in writing to get less. Raising SUM often costs a few dollars a month. In my experience it is the most valuable line on an auto policy, and the least examined.
The 90-day notice trap
UM and SUM claims carry a deadline that surprises almost everyone. Written notice to your own carrier is generally required within 90 days of the accident, or as soon as practicable. This is separate from the 30-day no-fault application. It is also separate from the three-year statute of limitations under CPLR § 214. Miss the notice requirement and the carrier can disclaim coverage entirely, no matter how strong the underlying claim.
Underinsurance cases spring this trap most often. People wait to see how the claim against the other driver develops before telling their own carrier anything. By the time the other policy proves inadequate, months have passed. The safer practice is to put every potentially involved carrier on notice early. For the full sequence of deadlines and early offers, see our guide to what happens in the weeks after you are hit in New York.
One structural point. A SUM claim runs against your own insurance company, usually through arbitration rather than a lawsuit. Your carrier weighs it like any contested claim: medical records, liability evidence, policy terms. Years of loyal premiums do not change the analysis.
How these claims fit the rest of New York law
UM and SUM claims for bodily injury still run through New York's no-fault framework. To recover pain and suffering, the injury must meet the serious injury threshold of Insurance Law § 5102(d): death, dismemberment, significant disfigurement, fracture, loss of a fetus, permanent loss of use of a body organ, member, function or system, permanent consequential limitation, or significant limitation of a body function or system. No-fault benefits themselves, up to $50,000 for medical bills and lost wages, come from the policy covering the vehicle you occupied and apply whether or not the other driver was insured.
Fault rules matter too. For actions started on or after May 26, 2026, CPLR § 1411 bars recovery in motor vehicle cases where the claimant's fault exceeds the combined fault of the parties recovery is sought against. Carriers evaluating SUM claims apply the same framework.
Two special situations deserve mention. Pedestrians and cyclists hit by uninsured or unidentified vehicles, with no auto policy in their household, may have a claim through MVAIC, the Motor Vehicle Accident Indemnification Corporation. MVAIC carries its own strict notice deadlines. And if an uninsured driver hit you while you were working, workers' compensation and the UM/SUM claim run on parallel tracks with lien issues between them. Our explainer on recovering beyond workers' comp covers how those tracks interact.
What to do now, before any crash
Pull your declarations page and find the SUM line. If it reads $25,000 per person, an underinsured driver can hurt you as badly as an uninsured one. Raising SUM to match your liability limits, or to $250,000 or more, is usually one of the cheapest changes you can make to a policy.
If a crash has already happened, the moves are different. Report it to the police the same day, especially if the other driver fled. Notify your own carrier in writing promptly, even if you believe the other driver was insured. File the no-fault application within 30 days. Do not accept the at-fault carrier's policy limit without first confirming, in writing, what SUM coverage sits behind it. Settling with the other driver without your own carrier's consent can forfeit the SUM claim entirely. Get that consent in writing before any release is signed.
