Stacked vs. Unstacked UM/UIM Coverage in California

By the FigureMyTax Editorial Team · How we calculate

In a state that allows stacking, each insured vehicle adds its uninsured and underinsured motorist limit to the total. California does not: its statute says the limits of two or more vehicles or policies may never be added together.

What stacking means

Many auto policies list a UM/UIM limit for each insured vehicle. Stacking adds those limits together after one injury, so a $100,000 limit on three vehicles becomes $300,000. Unstacked coverage pays only one limit. It matters only when your damages are larger than a single limit and larger than what the at-fault driver paid.

California says no

Insurance Code 11580.2(q) provides that, regardless of the number of vehicles involved, whether insured or not, persons covered, claims made, premiums paid or the number of premiums shown on the policy, in no event shall the limit of liability for two or more motor vehicles or two or more policies be added together, combined or stacked to determine the coverage available to injured persons. Paying a separate premium for each car does not change that.

A worked California example

Say your policy carries $100,000 of UM on each of three vehicles and an uninsured driver causes $250,000 of damages. A stacking state could pay up to $300,000, so the whole $250,000. California pays one limit: $100,000. If the driver were instead underinsured with a $30,000 policy, California UIM would pay up to your $100,000 limit less the $30,000 you received, so $70,000. Try your own numbers in the California UM/UIM stacking calculator.

What you can still combine

The ban is on adding limits, not on having more than one policy. A policy may provide that, if more than one UM coverage is available, your damages are not deemed to exceed the higher of the applicable limits and are pro-rated between the coverages by their limits (11580.2(d)). See what subdivisions (d) and (q) say together and how the underinsured test works.

A practical tip

Because stacking is unavailable, the most valuable choice is the UM/UIM limit itself. California requires insurers to offer UM at limits equal to your liability limits, up to $30,000 per person and $60,000 per accident, and UIM may be offered at higher limits (subdivisions (m) and (n)). Check your declarations page.

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