Does Arizona Allow UM/UIM Stacking? The Statute and the Supreme Court

By the FigureMyTax Editorial Team · How we calculate

Yes. Arizona permits stacking unless an insurer follows the single method in A.R.S. 20-259.01(H) and its policy plainly disavows it, and the Arizona Supreme Court has enforced that strictly in 2023 and again in July 2026.

The statutory text

Subsection (H) of A.R.S. 20-259.01 says that uninsured and underinsured motorist coverages are separate and distinct, and that if multiple policies or coverages purchased by one insured on different vehicles apply to an accident or claim, the insurer may limit the coverage so that only one policy or coverage, selected by the insured, applies to any one accident. If the policy does not tell the insured of the right to select, the insurer must notify the insured in writing within 30 days after it receives notice of the accident. "Insurer" includes every insurer within a group under common management.

Franklin v. CSAA (2023)

In Franklin the Court held that a multi-vehicle policy provides a separate UIM coverage for each vehicle and that subsection (H) is the sole means for insurers to limit stacking, whether within a policy or across policies. It wrote that insurers cannot avoid the statute by defining UIM as one coverage in the policy. The same decision is reported in a public case-law database.

The 30-day notice is not a loophole

The insurer in Franklin argued that the 30-day notice in subsection (H) lets it prevent stacking after an accident regardless of the policy's wording. The Court rejected that reading, emphasizing that, to prevent stacking, insurers must include in the policy unambiguous language plainly disavowing the possibility of stacking.

State Farm v. Balzan (2026)

In State Farm v. Balzan, decided July 6, 2026, the Court restated that stacking is permitted unless the policy contains clear and unambiguous language prohibiting it. It then held that multiple insured individuals who jointly purchase multiple policies from the same insurer are "one insured" under subsection (H), so a clear anti-stacking clause can limit them to one coverage. A household with several State Farm policies, for example, can be limited if the clause is clear.

Other rules in the statute

An insurer may require all vehicles it insures for the same named insured to have the same UM/UIM limits (20-259.01(C)). Arizona also treats a multi-policy household differently depending on who bought what, so ask your insurer in writing which clause it relies on. A defense-firm guide notes that stacking across policies from different companies is treated as permissible; we did not verify the underlying decision.

What to do with this

Find your policy language, then use the Arizona UM/UIM stacking calculator with and without a clear anti-stacking clause. If you are new to the terms, start with stacked versus unstacked coverage.

This is general information, not legal advice, and the state comparisons above are illustrative, not an exhaustive survey. Confirm how Arizona's rules apply to your specific case with a licensed Arizona attorney.