Underinsured motorist arizona coverage exists for one specific situation: the other driver hit you, totaled your car, left you with $80,000 in medical bills, and their 25/50 policy just handed you a check for $25,000. If you want to understand every coverage type that affects you on Arizona roads, start with the arizona insurance guide that maps the full picture.
Key Takeaways:
- Arizona UIM coverage fills the gap between what the at-fault driver’s liability policy pays and your actual damages, but only if you didn’t sign an opt-out form under ARS 20-259.01.
- Arizona’s minimum liability limits are 25/50/15, meaning the at-fault driver owes you at most $25,000 per person in bodily injury, a figure that covers roughly one night in a trauma ICU.
- You must exhaust the at-fault driver’s liability policy before your UIM coverage pays, claim sequencing determines how fast and how much you collect.
What Underinsured Motorist Coverage Actually Does in Arizona
Underinsured motorist coverage, or UIM, is the portion of your own auto policy that pays the difference between what the at-fault driver’s liability insurance covers and your actual damages. This means when another driver causes your injuries but their policy limit runs out before your bills do, your UIM coverage steps in to close that gap, up to your own UIM limit.
Here’s the mechanic in plain terms. The at-fault driver’s bodily injury liability limit is the floor. Your UIM limit is the ceiling. UIM pays what falls between those two numbers, subject to your own policy’s terms.
UIM is not a duplicate payment. It does not pay alongside the other driver’s policy. It only activates after the other driver’s coverage is fully exhausted. If the at-fault driver carries $25,000 per person and your injuries cost $90,000, their carrier pays $25,000 first. Your UIM carrier then looks at the remaining $65,000 and pays up to whatever UIM limit you purchased.
UIM is also distinct from UM, uninsured motorist coverage. UM applies when the at-fault driver has no liability insurance at all. UIM applies when they have insurance but not enough. Both coverages are governed by ARS 20-259.01, which requires Arizona carriers to offer them together, but each activates under different conditions. You can have one without the other, though most policies bundle them.
Arizona’s minimum bodily injury liability is $25,000 per person under ARS 28-4009. In a serious crash, that figure covers roughly one ambulance ride and one emergency room visit. Anything beyond that, surgery, hospitalization, rehabilitation, lost wages, lands on the injured party unless UIM coverage is in place.
The Real-World Math: How the UIM Gap Hits You
The gap between what minimum-coverage drivers can pay and what a serious injury costs is not theoretical. It shows up in claim after claim, and the math is not complicated once you see it laid out.
Arizona’s 25/50/15 minimum liability structure means the worst-case payout from an at-fault driver with minimum coverage is $25,000 per person bodily injury and $15,000 property damage. Those numbers were set decades ago and have not kept pace with medical inflation. A single night in a trauma ICU can exceed $25,000 before any surgeon or specialist bills arrive.
Here is how UIM math works across three common at-fault driver scenarios against a $150,000 injury bill:
| At-Fault Driver’s Liability Limit (per person) | What Their Policy Pays | Your Remaining Damages | What UIM Must Cover |
|---|---|---|---|
| $25,000 (minimum) | $25,000 | $125,000 | Up to your UIM limit |
| $50,000 | $50,000 | $100,000 | Up to your UIM limit |
| $100,000 | $100,000 | $50,000 | Up to your UIM limit |
If your UIM limit is $100,000 and the at-fault driver carried minimum 25/50, your UIM carrier owes you $100,000 on top of the $25,000 you already collected, for a total recovery of $125,000 against a $150,000 bill. You still absorb $25,000 out of pocket. If your UIM limit is $50,000, your total recovery is $75,000. The gap you personally eat depends entirely on the UIM limit you chose when you bought the policy.
The 25/50 scenario is not the edge case. It’s the most common one on Arizona roads because minimum limits are the legal floor, and a significant portion of AZ drivers carry exactly that. When you’re deciding how much UIM to carry, the question of how much uninsured motorist coverage you need in arizona runs through the same math, your UIM limit is what determines the ceiling of your own protection.
Carrying UIM limits below your liability limits is a common mistake. If you carry $100,000 per person in liability but only $25,000 in UIM, you’re fully exposed in the scenario where someone with minimum coverage causes a six-figure injury to you or a passenger.
Is Underinsured Motorist Coverage Required in Arizona?
UIM is not mandatory on your policy. What is mandatory is that your carrier offer it. ARS 20-259.01 requires Arizona insurers to include UM/UIM coverage at limits equal to your liability coverage unless you sign a written rejection. The coverage defaults on. You have to take a deliberate step to remove it.
That written rejection is called a UM/UIM opt-out form. It typically appears buried inside a policy application or a renewal packet, sometimes as a single page among dozens. Agents working volume tend to walk applicants through it quickly, if at all. The signature gets collected and the waiver goes into the file.
The binding effect of that signature is not limited to the first policy term. A signed waiver on a prior policy carries forward unless you revoke it in writing. Under ARS 20-259.01, the rejection must be signed by the named insured, a verbal rejection is not valid. But once a valid written waiver exists, it does not expire on its own.
This creates a specific problem. Policyholders who signed an opt-out form three renewals ago, changed carriers, moved, or simply don’t remember often assume they have UIM because they’ve been paying premiums. The declarations page tells you the truth. If you’ve never checked it for a UM/UIM line item, you may be carrying no UIM at all.
A second version of this problem is reduced-limit UIM. ARS 20-259.01 allows carriers to offer UIM at limits lower than your liability limits if you accept them in writing. Many policyholders accept without understanding the tradeoff. They technically have UIM, it’s just capped at a number that won’t cover a serious crash.
The practical read: most people who believe they have full UIM protection either waived it on a form they don’t remember signing, or accepted a reduced limit they didn’t notice was lower than their liability coverage.
Claim Sequencing: You Have to Exhaust Their Policy First
Claim sequencing is the part of UIM that surprises injured policyholders most. Your UIM coverage does not activate the moment you’re hurt. It activates after a specific series of steps, in a specific order, and skipping a step can cost you the entire UIM payout.
UIM claim sequencing requires full exhaustion of the at-fault driver’s liability limits before your own UIM coverage activates. That means the process runs in stages:
File against the at-fault driver’s liability carrier. This is your first claim. You pursue their bodily injury liability coverage for your medical expenses, lost wages, and damages. Do not contact your own carrier for UIM before this step is underway.
Collect whatever that policy pays. The at-fault driver’s carrier will typically pay at or near its per-person limit once your damages exceed that amount. Document every payment and retain the settlement correspondence.
Notify your own carrier of the UIM claim before settling with the at-fault driver. This step is where most people make a costly mistake. Settling the at-fault driver’s liability claim without notifying your own carrier first can trigger a policy condition that voids UIM coverage entirely, this clause appears in standard AZ auto policy forms. Your carrier must have the opportunity to protect its subrogation rights before you release the at-fault driver from liability.
Allow your carrier to evaluate the remaining damages. Once the at-fault driver’s policy is exhausted and your carrier has been properly notified, your UIM carrier reviews your total documented damages, subtracts what you already received, and pays up to your UIM limit on the remaining balance.
Understand that your carrier has subrogation rights. In some situations, your carrier must consent to a settlement that releases the at-fault driver for less than their full limits. If you accept a lowball settlement from the at-fault driver’s carrier without that consent, you may forfeit UIM entirely.
The timeline pressure is real. At-fault carriers often push for fast settlements because a quick release locks in a lower payout. If you’re seriously injured, the UIM claim is worth more than a fast check from the at-fault driver’s carrier. Slow down, notify your own carrier, and let the sequence run in order.
How Do I Know If I Have Underinsured Motorist Coverage on My Arizona Policy?
Your Arizona auto policy declarations page shows UM/UIM limits as a separate line item when coverage is active. If it isn’t there, the coverage isn’t there. Here is how to check right now:
Pull your declarations page and look for a line labeled UM or UIM. It will show a dollar amount per person and per occurrence if coverage is active. The declarations page is the one-page summary at the front of your policy packet, not the full policy document.
If the line is missing, reads ‘rejected,’ or reads ‘waived,’ you opted out. That waiver is still binding unless you’ve revoked it in writing. You can add UIM back at your next renewal, but it will not apply to any claim already in progress.
Check whether your UIM limit matches your liability limit or sits below it. A lower UIM limit means you accepted a reduced offering at some point. A policy with $100,000 per person in liability and $25,000 in UIM leaves a wide gap uncovered.
If you have multiple vehicles on the same policy, check each vehicle’s UM/UIM listing separately. Arizona permits UM/UIM stacking across multiple vehicles on the same policy unless the policy explicitly prohibits it, stacking can meaningfully change the maximum payout available on a single claim. Two vehicles each with $100,000 UIM on a stackable policy gives you $200,000 in effective UIM coverage on one claim. Not all policies allow it, and carriers can restrict stacking in the policy language.
Check your signed application for a UM/UIM rejection form if you suspect you waived it. Your carrier keeps a copy on file. Ask for it directly. If a rejection form exists with your signature, it is binding.
If your declarations page shows UIM limits that seem random, $15,000 when your liability is $100,000, for example, call and ask when and why that limit was set. It likely traces back to a reduced-limit offer you accepted without a full explanation of the consequences.
Frequently Asked Questions
What is the difference between uninsured and underinsured motorist coverage in Arizona?
Uninsured motorist coverage pays when the at-fault driver has no liability insurance at all. Underinsured motorist coverage pays when the at-fault driver has insurance but their limits are too low to cover your damages. Under ARS 20-259.01, Arizona carriers must offer both coverages together, though each activates under different conditions, UM for the driver with nothing, UIM for the driver with not enough.
Can I add underinsured motorist coverage to my Arizona policy after I’ve already been in an accident?
No. UIM coverage must be active at the time of the accident, you cannot add it retroactively after a crash has already occurred. If you signed an opt-out form under ARS 20-259.01 and want UIM reinstated, you can do that at your next renewal, but it will not apply to a claim already in progress.
Does underinsured motorist coverage pay for property damage in Arizona?
Standard UIM coverage applies to bodily injury, medical bills, lost wages, and pain and suffering. Uninsured motorist property damage, or UMPD, is a separate add-on that covers vehicle damage when the at-fault driver has no property damage liability coverage. Arizona’s minimum property damage liability limit is $15,000, so UMPD becomes relevant when your vehicle damage exceeds that figure and the at-fault driver only carries minimum coverage.
