Arizona’s Supreme Court is NOT done rewriting the UM/UIM stacking playbook. In fact, stacking just got more complicated in Arizona — and the rulebook keeps shifting under insurers’ feet.
A few years ago, in Franklin v. CSAA Gen. Ins. Co. (2023), the Arizona Supreme Court held that a single policy covering multiple vehicles is presumed to provide separate UIM coverage for each vehicle. Translation: intra-policy stacking is available by default, and insurers can only defeat it by satisfying A.R.S. § 20-259.01(H) — clear anti-stacking language in the policy PLUS proper notice of the insured’s right to select one coverage. Silence or clever policy drafting won’t cut it. As a result, carriers were left trying to ensure the right to select coverage was communicated clearly at the appropriate time.
This month, in State Farm Mut. Auto. Ins. Co. v. Balzan (2026), the Court tackled the flip side: inter-policy stacking among family members. The question was whether multiple named insureds (there, a married couple) who jointly purchase several policies from the same insurer count as “one insured” under § 20-259.01(H). The Court said yes — when named insureds act together to procure coverage, they function as a single purchasing unit, and the anti-stacking clause applies to limit them to one selected policy. A son with his own separate policy, though, wasn’t swept into that same limitation.
Taken together, these decisions sketch out where the current line sits in Arizona:
Multi-vehicle, single-policy scenarios: stacking is presumed unless the insurer’s policy language and notice strictly comply with § 20-259.01(H).
Multiple policies jointly purchased by co-insureds (think spouses, household policies): those insureds are treated as one purchasing unit, and stacking across their jointly bought policies can be limited.
If you have questions about how these holdings might affect current UM/UIM policy forms or claims-handling practices in Arizona, please connect with JP directly at jharrington@cm.law.
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The foregoing content is for informational purposes only and should not be relied upon as legal advice. Federal, state, and local laws can change rapidly and, therefore, this content may become obsolete or outdated. Please consult with an attorney of your choice to ensure you obtain the most current and accurate counsel about your particular situation.
