Stacked vs. Unstacked Car Insurance

Stacked and unstacked car insurance refer specifically to how uninsured/underinsured motorist (UM/UIM) bodily injury coverage works across multiple vehicles or policies. Stacked coverage combines the UM/UIM limits from each vehicle or policy you're named on, giving you a larger pool of coverage after an accident with an uninsured driver. Unstacked coverage keeps those limits separate, so you only draw from the limit on the vehicle involved in the crash.

UM/UIM stacking applies to bodily injury coverage only, not property damage. If an uninsured driver hits your car and injures you, stacking can increase the medical compensation available to you. It won't increase what your policy pays to repair your vehicle.

Most car insurance policies with UM/UIM coverage are unstacked by default. You have to opt in to stacking if your state and insurer allow it, which raises your premium.

Stacked car insurance lets you combine UM/UIM bodily injury coverage limits across multiple vehicles on one policy or across multiple policies on which your name appears. For example, if you have a $25,000 UM limit on one car and $50,000 on another, stacking gives you up to $75,000 in total coverage if an uninsured driver injures you.

There are two types of stacking: vertical (within one policy) and horizontal (across multiple policies).

Unstacked car insurance limits your UM/UIM bodily injury coverage to the vehicle involved in the accident. Even if you own multiple cars or live with another insured driver, the coverage limits don't combine. Your payout after an accident with an uninsured driver is capped at the amount listed on your policy's declarations page for that one vehicle.

Unstacked coverage is the standard default on most auto policies. Its main advantage is cost, as premiums are lower than stacked coverage. The tradeoff is lower financial protection if your medical costs from an accident with an uninsured driver exceed your per-vehicle limit. Eighteen states prohibit stacking entirely. See the full state breakdown below.

Stacking isn't available everywhere. Some states prohibit it entirely, some allow only one type and others permit both vertical and horizontal stacking. Even in states that allow stacking, individual insurers can decline to offer it. Confirm with your carrier before assuming stacking is an option.

States where stacking is not permitted: Alaska, Arizona, California, Connecticut, Idaho, Illinois, Iowa, Kansas, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Nebraska, North Dakota, South Dakota, Washington.

Stacking makes financial sense in specific situations. The added premium is most justified when your exposure to uninsured drivers is higher than average or when your current UM/UIM limit would fall short of covering a serious injury.

Drivers in states that don't allow stacking still have ways to strengthen financial protection after an accident with an uninsured or underinsured driver. The options below work in every state and can be combined to close the gap that stacking would otherwise fill.

Stacked insurance increases your UM/UIM bodily injury coverage by combining limits across vehicles or policies, giving you more financial protection if an uninsured driver injures you. It costs more than unstacked coverage and isn't available in every state or from every insurer. Owners of multiple vehicles, drivers in states with high rates of uninsured motorists and those who regularly carry passengers should price out stacking before deciding. For single-vehicle owners or drivers in lower-risk states, unstacked coverage provides adequate protection at a lower cost.

Stacked insurance can help protect you in the event of an accident. Questions about insurance stacking:

Why Trust MoneyGeek? 

MoneyGeek has a team of expert writers, researchers, editors and fact-checkers to ensure readers receive easily comprehensible and accurate content. Each MoneyGeek article is subject to our review methodology, editorial process, and policy, which include research, writing, editing, fact-checking and publication. Our editorial team thoroughly fact-checks sources. A thorough review procedure ensures we maintain high editorial standards in every published article. 

We research topics and frequently ask questions, design and publish content, and offer informative, trustworthy and unbiased financial advice. The methodologies employed in the content on many MoneyGeek pages are validated and verified by subject matter experts.