What Does UM/UIM Coverage Actually Protect You From?

Why This Coverage Exists

Despite Arizona’s minimum insurance requirements (generally 25/50/15, meaning $25,000 per person and $50,000 per accident for bodily injury, and $15,000 for property damage), some drivers remain uninsured entirely, or carry only the state minimum, which falls far short of covering a serious injury. UM/UIM coverage exists specifically to protect you in these situations.

This gap matters more than most people realize. A single serious injury, a fracture requiring surgery, an extended hospital stay, can easily exceed $25,000 in medical costs alone, without accounting for lost wages or pain and suffering.

How UM Coverage Works

If you’re hit by a driver with no insurance at all, or in a hit-and-run where the driver cannot be identified, your own UM coverage can step in to cover your damages, up to your policy limit. This coverage effectively treats an uninsured or unidentified driver similarly to how a claim against an insured driver would work.

Filing a UM claim generally involves demonstrating the same things you would need to prove against an at-fault driver directly: that the other driver was negligent, and the extent of your resulting damages.

How UIM Coverage Works

If the at-fault driver has insurance, but their policy limit is not enough to cover your full damages, UIM coverage can make up the difference, up to your own policy’s UIM limit. This is a common scenario when a driver carries only Arizona’s state minimum coverage.

A UIM claim typically proceeds after the at-fault driver’s own policy limits are exhausted, meaning you generally need to resolve that portion of the claim first before turning to your own UIM coverage for the remaining gap.

Checking Whether You Have This Coverage

Since Arizona allows policyholders to decline UM/UIM coverage in writing, review your policy declarations page or contact your insurance agent to confirm whether you actually carry it, before you need it. Many drivers assume they have this coverage automatically and are surprised to learn otherwise after an accident.

If you do not currently have this coverage, it is worth discussing with your insurance agent whether adding it makes sense, given how common underinsured drivers actually are on Arizona roads.

Stacking and Multiple Vehicle Policies

Depending on your policy structure, if you have UM/UIM coverage on multiple vehicles, you may be able to combine or “stack” that coverage in some circumstances, increasing the total available protection. Whether this applies depends heavily on your specific policy language and should be reviewed carefully with an attorney.

This is a detail many policyholders never think to check, and it can meaningfully change the total coverage actually available in a serious injury case.

Why This Often Becomes an Adversarial Claim, Even Against Your Own Insurer

It can feel counterintuitive, but a UM/UIM claim is technically a claim against your own insurance company, and insurers do not automatically treat these claims more generously just because you have been a loyal customer. Your own insurer can still dispute the value of your damages or the extent of the other driver’s fault.

This is exactly why having legal representation for a UM/UIM claim matters as much as it would for a claim against a stranger’s insurance company.

Steps to Take if the At-Fault Driver May Be Uninsured or Underinsured

1. Confirm your own UM/UIM coverage by reviewing your policy or calling your agent.
2. Document the accident thoroughly, just as you would for a claim against an insured driver.
3. Report the claim to your own insurer promptly, most policies have notice requirements.
4. Have an attorney review the claim before accepting any offer from your own insurance company.