Before accepting any settlement from your own insurer, it is worth knowing whether Arizona law lets you combine, or "stack," more than one uninsured or underinsured motorist policy. Big Auto Accident Attorneys has built its practice around exactly this kind of insurer pushback, regularly turning initial settlement offers into recoveries many times larger once every available policy is accounted for. The firm's attorneys see this question come up often, especially in households with multiple cars or multiple policies, and the answer has shifted with recent Arizona Supreme Court rulings. Here is what stacking means, what the statute allows, and why it matters before you sign anything.
What Does It Mean to "Stack" UM/UIM Coverage?
Stacking means combining the uninsured motorist (UM) or underinsured motorist (UIM) limits from multiple policies to increase the total amount available after a crash.
Arizona courts, as explained in Franklin v. CSAA General Insurance Co., distinguish between two types of stacking:
- Intra-policy stacking: Combining coverages for multiple vehicles insured under a single policy.
- Inter-policy stacking: Combining coverages from entirely separate policies.
What Does Arizona Law Say About Stacking?
Arizona's Uninsured/Underinsured Motorist Act (A.R.S. § 20-259.01) generally allows stacking unless an insurer's policy complies with the anti-stacking provision in subsection (H).
That subsection permits an insurer to limit a claimant to a single policy or coverage when:
- Multiple policies or coverages were purchased by one insured from the same insurer
- Those policies or coverages apply to different vehicles
- All of those vehicles are involved in, or that coverage applies to, the same accident or claim
When those conditions are met, the insurer may require the claimant to select just one policy or coverage to apply. If the insured or a resident relative purchased policies from different insurance companies, those companies cannot prevent stacking of the coverage.
Can You Stack Coverage Across Multiple Vehicles on One Policy?
Generally, no. If an insurer follows the Arizona statutes and clearly notifies the insured that multiple vehicle stacking is prohibited, that prohibition is enforceable. Nearly all insurers in Arizona know the law and include anti-stacking provisions in their policies. If an insurer fails to follow the law, as in Franklin v. CSAA General Insurance Co., the Arizona Supreme Court held that:
- An auto policy insuring multiple vehicles provides separate UIM coverage for each vehicle, rather than one coverage that applies across all of them
- An insured can recover UIM benefits greater than the bodily injury limits shown on the declarations page by stacking those separate coverages
- This stacking is only barred if the insurer's policy language strictly complies with the anti-stacking requirements of subsection (H)
Can You Stack Coverage from Policies Purchased by the Same Household?
In State Farm Mutual Automobile Insurance Co. v. Balzan, decided in July 2026, the Arizona Supreme Court held that multiple family members who jointly purchase several household policies from the same insurer count as "one insured" under A.R.S. § 20-259.01(H).
As a result, an insurer can still limit stacking across those jointly purchased household policies, even though the policies covered different vehicles and different named drivers.
Can You Stack UM and UIM Coverage Together?
Generally, no. Arizona treats uninsured and underinsured motorist coverage as separate remedies for distinct situations, and a claimant typically applies one or the other to a given loss rather than combining them. UM and UIM benefits also cannot be accessed until other applicable coverage, including the at-fault driver's own liability policy, has been exhausted first.
Why This Matters Before You Accept a Settlement
Insurers do not always volunteer whether a claimant is entitled to stack available coverage, and once a settlement is signed, that decision is usually final. Before agreeing to any number, it helps to know:
- How many vehicles and policies are on the household's declarations pages
- Whether the policy language strictly complies with A.R.S. § 20-259.01(H)
- Whether the policies were purchased by one person or jointly by multiple household members
- Whether any liability or UIM coverage has already been exhausted
Why Talk to Big Auto Before Settling a UM/UIM Claim
Whether you can stack UM or UIM coverage in Arizona depends on how your household's policies were purchased and whether the insurer's anti-stacking language complies with A.R.S. § 20-259.01(H). These questions are easy to get wrong without a close read of the declarations pages and endorsements. Big Auto's attorneys review every available policy before a settlement is accepted, so a claimant does not leave stackable coverage on the table simply because an insurer did not raise it. Call 1 (844) BIG-AUTO for a free case evaluation, and know the full value of what is actually available before you settle.
Disclaimer: The information on this page is provided for general educational purposes only and does not constitute legal advice. Every case is different. Past results do not guarantee future outcomes.
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