California's "notice-prejudice" rule (Cal. Ins. Code § 554) provides that an insurer may deny a late claim only if:

• Any notice provided after the policy expiration date is automatically late
• The insured failed to report the claim in writing rather than orally
• The insured filed the claim more than 30 days after the loss
• The insured's late notice actually prejudiced the insurer's ability to investigate or defend