California Does Not Require Underinsured Motorist Coverage
California does not mandate underinsured motorist (UIM) coverage. Underinsured motorist protection is optional.
Every carrier writing auto insurance in California must offer UIM coverage on every policy, but you can reject it. The rejection must be in writing. When you insure multiple vehicles on one policy, that rejection applies to every car on the policy — not vehicle by vehicle.
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Get Your Free QuoteCalifornia Uninsured Motorists
20.4%
One in five California drivers carries no insurance. When an uninsured or underinsured driver hits you, UIM coverage pays your medical bills and lost wages up to your policy limit.
Insurance Information Institute, 2023
How Underinsured Motorist Coverage Works on a Multi-Car Policy
Underinsured motorist coverage pays when the at-fault driver's liability limit is lower than your damages. California is a fault state: the at-fault driver's insurer pays your claim.
On a multi-car policy, UIM coverage applies per accident, not per vehicle. The limit does not multiply by the number of vehicles on the policy.
When you add a vehicle to an existing policy, the UIM coverage you already selected extends to the new car automatically. You do not choose UIM separately for each vehicle. If you rejected UIM when you opened the policy, the rejection carries forward to every vehicle you add later.
Rejecting UIM in writing removes coverage from every vehicle on the policy. You cannot reject it for one car and keep it on another.
What Carriers Must Offer When You Add UIM
You can accept that amount, request a lower limit, or reject UIM entirely. All three choices require a signature. The carrier cannot sell you a policy without documenting your UIM decision.
When you combine two household policies into one multi-car policy, the carrier re-offers UIM at the combined policy's liability limit. You make a new UIM election that applies to every vehicle and every driver on the merged policy.
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Rejecting UIM Does Not Lower Your Premium as Much as Dropping Collision
UIM coverage costs less than collision or comprehensive coverage because it pays only when another driver is at fault and underinsured. Collision pays regardless of fault. Comprehensive pays for theft, weather, and animal strikes. Both coverages tie to your vehicle's value; UIM ties to medical costs and lost wages.
Dropping collision on an older car with low market value saves more than rejecting UIM. The coverage gap UIM closes is larger than the gap collision closes on a low-value vehicle.
When you insure four vehicles on one policy and two are older cars, you can drop collision on the older two and keep UIM across the entire policy. That combination reduces premium more than rejecting UIM and keeping collision on all four.
California Average Annual Auto Expenditure
$1,223.16
California drivers spent an average of $1,223.16 per insured vehicle in 2023. Multi-car policies typically lower the per-vehicle cost through the multi-car discount, which requires every vehicle on the same policy.
NAIC Auto Insurance Database Report, 2023
UIM Stacks in California Only When You Buy Stacked Coverage
California allows stacked UIM coverage, but it is not automatic. Stacked coverage lets you combine the UIM limits from multiple vehicles on your policy.
Stacked UIM costs more than unstacked. Carriers price it by multiplying the per-vehicle premium by the number of vehicles. The decision matters most for households with multiple drivers who could be injured in the same accident.
Compare Carriers That Write Multi-Car Policies in California
California's carrier roster includes 27 insurers writing multi-car policies. Liability insurance is mandatory; UIM is optional but must be offered. Carriers differ in how they price UIM on multi-car policies, whether they offer stacked coverage, and how the multi-car discount applies when you add or remove vehicles.
Compare quotes with UIM included and with UIM rejected. The difference shows what the coverage costs across your household's vehicles. Request quotes from carriers that write your household's vehicle count and driving profiles, and confirm whether the multi-car discount applies before or after UIM is added.