Auto Insurance
Stacking (UM/UIM)
Combining UM/UIM limits across multiple vehicles or policies to increase the total protection available.
Last reviewed: May 2026 · Editorial methodology
Definition
Stacking allows you to add together the uninsured/underinsured motorist (UM/UIM) limits from multiple vehicles or policies to create a larger coverage pool. For example, if you own three vehicles each with $100,000 in UM coverage, stacked coverage provides up to $300,000 per accident. Interstate stacking — combining policies from multiple insurers — is less common and more complex than intra-policy stacking. About half of U.S. states permit stacking; others prohibit it or allow insurers to include anti-stacking language. Florida and Pennsylvania explicitly allow it, while California generally does not. Stacked coverage costs more but significantly improves protection in serious accidents.
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Cover Forge USA Editorial Team
Editorial Lead
This article was researched and written by the Cover Forge USA editorial team against federal sources (NAIC, CMS, FEMA, DOL, SSA, state DOIs) and standard policy forms. Bylines organize content by topic — they do not assert individual licensure. See our editorial-policy for details.
Reviewed 2026-06-14
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