Question: What do stacked and non-stacked mean?

Answer: Stacking normally refers to an option you can select for uninsured motorist bodily injury (UM) and/or underinsured motorist bodily injury (UIM) coverages. 

Stacking uninsured motorist coverage and/or underinsured motorist policies is an option that allows you to increase the limits you select for your UM/UIM bodily injury coverage. Limits increase based on the number of cars you are insuring. For this increased level of protection, you will pay a higher car insurance premium.

Here is an example of stacking:

John has limits of $100,000 per person and $300,000 per accident (written as 100/300) for his uninsured motorist bodily injury coverage and is insuring two vehicles. If he leaves them “unstacked,” or non-stacked as you called it, John’s limits would stay at 100/300. Instead, if John chose to stack his UM coverages, his limits would double to $200,000 per person and $600,000 per accident (200/600).

By selecting stacking for your uninsured/underinsured motorist bodily injury coverage, you simply increase your limits for each coverage by the number of cars you insure. Generally, there is not limit on the number of vehicles that can be insured and, thus, stacked this way.

The Property Casualty Insurance Association of America (PCIAA) lists nearly 30 states whose statutes, rules, and/or case law either do not address the issue or specifically allow stacking. However, in many states that allow stacking, auto insurers are permitted to include policy language that prevents policyholders from stacking UM/UIM coverage. So, while your state might permit stacking, if your policy explicitly forbids it, you will not be able to stack your benefits.

Since laws in each state vary widely for UM/UIM stacking in accordance with each situation and sometimes depending upon case law plus state insurance laws are continually being changed and updated, it is best to check with your state’s insurance regulator or your insurance agent to find out if you can stack your UM/UIM benefits.

Stacking within one policy vs stacking across policies

When you stack UM and UIM coverages, you have two options: stack within one policy or stack across policies.

Stacking within one policy means you can stack your uninsured and/or underinsured bodily injury coverage when you have more than one car on the same policy. So, if you have four cars on your auto policy, each with UM limits of $100,000, you can choose to stack these and combine the coverage limits for a total limit of $400,000.

Stacking across policies works if you have two or more separate auto policies for your household vehicles. If you have $100,000 per person UM limits on each vehicle and are hit by an uninsured driver, you can file a claim under each car’s policy. Thus, if you have two separate policies in this scenario and your damages come to $150,000, you can make a $100,000 claim under the first car’s UM coverage and then a second claim for the remaining $50,000 under your second car’s UM coverage. 

A reason to stack your coverages is to obtain much higher limits for UM and UIM coverage. However, if you’re pinching pennies, you may want to hold off on stacking since you’ll pay more for the privilege (because your car insurance company could possibly have to payout more if you used your UM/UIM coverage). 

 — Michelle Megna contributed to this story.

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Contributing Writer

Prachi is an insurance writer with a master’s degree in business administration. Through her writing, she hopes to help readers make smart and informed decisions about their finances. She loves to travel and write poetry.