About UM/UIM claims in California: When the other driver has no insurance (uninsured motorist or "UM") or not enough insurance (underinsured motorist or "UIM"), California law requires most auto policies to include coverage that protects you. Insurance Code § 11580.2 mandates UM/UIM coverage equal to your liability limits unless you specifically reject it in writing.
Unlike a standard third-party claim against the at-fault driver's insurer, a UM/UIM claim is against your own insurance company. This creates unique dynamics: consent-to-settle clauses, arbitration rights, bad-faith exposure, and different negotiation strategies.
I'm a California-licensed attorney who handles UM/UIM demand letters and arbitrations personally. This guide covers how California UM/UIM claims work, how to write effective demand letters, when arbitration or litigation is appropriate, and how Prop 213 and other California rules affect your claim. For broader car accident demand guidance, see the main California car accident demand letters guide.
California's UM/UIM framework protects you when:
| UM (Uninsured) | UIM (Underinsured) |
|---|---|
| At-fault driver has zero liability coverage | At-fault driver has some coverage, but not enough |
| Includes hit-and-run if physical contact occurred | Requires proof other driver's limits are insufficient |
| No "exhaustion" requirement | Must accept the other driver's policy limits first (exhaustion) |
| Your UM limits are available immediately | Your UIM recovery = (your UIM limit - other driver's limit paid) |
Your "dec page" lists all coverages and limits. Look for:
If you insure multiple vehicles on the same policy, California allows stacking of UM/UIM limits if your policy language permits. Most modern policies include anti-stacking clauses. Check the UM/UIM section of your policy for language like:
Insurance Code § 11580.2(h) requires you to obtain your UM/UIM carrier's written consent before settling with an underinsured at-fault driver. Your policy will have a clause like:
"No settlement with any person or organization alleged to be legally liable for the bodily injury shall be made without our written consent."
Violation = forfeiture of UIM claim. Always notify your carrier before accepting any settlement from the at-fault driver's insurer.
Most California UM/UIM policies include mandatory arbitration clauses. Typical language:
"If we and the insured do not agree on the amount of damages, either party may demand arbitration. Arbitration shall be binding and shall be conducted in accordance with the rules of the American Arbitration Association."
Arbitration is generally faster and cheaper than litigation, but you lose the right to a jury trial. Either you or the insurer can demand arbitration; the other party cannot refuse.
Scenario: You are rear-ended at a stoplight. Other driver has no insurance. You have $100K UM coverage. Injuries: herniated disc, $40K medical bills (Howell-adjusted to $18K actually paid), $5K wage loss, pain-and-suffering claim $30K.
Claim process:
Scenario: Head-on collision, other driver 100% at fault. Other driver has $15K policy limit. Your damages: $80K. Your UIM limit: $100K.
Claim process:
Most California UM/UIM policies include mandatory arbitration clauses governed by Code of Civil Procedure § 1281 et seq. Either you or the insurer can demand arbitration if you disagree on the amount of damages (assuming liability and coverage are not in dispute).
Your own insurer owes you an implied covenant of good faith and fair dealing (Comunale v. Traders & General Insurance Co., 50 Cal.2d 654 (1958)). If the insurer unreasonably denies or delays your UM/UIM claim, you can sue for breach of the covenant (bad faith), which allows recovery of:
I am a California-licensed attorney who personally handles uninsured and underinsured motorist claims. UM/UIM claims involve unique procedural requirements (consent-to-settle, exhaustion, arbitration rights) and California-specific legal rules (Howell, Prop 213, bad-faith exposure) that demand careful attention.
I also assist insurance carriers and third-party administrators in evaluating and defending UM/UIM claims to avoid bad-faith exposure.
You can handle a straightforward UM/UIM claim yourself if liability is clear, damages are well-documented, and you understand Howell adjustments and Prop 213. However, UM/UIM claims involve technical requirements (consent-to-settle, exhaustion, arbitration clauses) that are easy to violate. An attorney is advisable if:
If your carrier denies coverage, first confirm the denial is in writing and understand the stated reason (e.g., "no coverage under policy," "comparative negligence bars recovery," "Prop 213 applies"). Common responses:
Uncontested claim: 30-90 days from demand letter to settlement if the carrier agrees liability and damages are clear.
Negotiation: 3-6 months if there is back-and-forth on valuation but no arbitration.
Arbitration: 6-12 months from demand to arbitration hearing and award. AAA/JAMS arbitrations are faster than litigation but require scheduling an arbitrator and conducting discovery.
Bad-faith litigation: 1-3 years if you must sue the carrier in superior court for unreasonable denial. Most bad-faith cases settle before trial once the insurer faces discovery and punitive damages exposure.
California allows stacking of UM/UIM limits across vehicles on the same policy if the policy language permits it. Most modern policies include anti-stacking clauses like: "The most we will pay is the single highest limit for any one vehicle you own."
Check your policy's UM/UIM section. If it is silent on stacking, California courts have historically allowed it. If it explicitly prohibits stacking, you are limited to the single highest limit.
Example (stacking allowed): You insure two cars, each with $100K UM. You are injured as a pedestrian by an uninsured driver. You can claim $200K total ($100K + $100K).
Example (stacking prohibited): Same scenario, but policy says "no stacking." You can only claim $100K (the limit for one vehicle).
Insurance Code § 11580.2(h) requires you to obtain your UM/UIM carrier's written consent before settling with an underinsured at-fault driver. If you settle without consent, the carrier can deny your entire UIM claim—even if the settlement was reasonable.
How it works:
Trap: If you accept a check from the at-fault driver's insurer before getting consent, you may forfeit your UIM claim entirely. Always notify your carrier first.
Yes. Proposition 213 (Civil Code § 3333.4) bars uninsured drivers from recovering non-economic damages (pain-and-suffering, emotional distress) in any vehicle accident claim, including UM/UIM claims against their own insurer.
What it means: If you did not have liability insurance at the time of the accident, you can only recover economic damages (medical expenses, wage loss, property damage) from your UM/UIM carrier. You cannot recover pain-and-suffering even if the other driver was 100% at fault.
Exception: Prop 213 does not apply if the at-fault driver was convicted of DUI or was fleeing from a felony at the time of the accident.