California's 90-Day Rule and Good-Faith Investigation

California Labor Code 5402 requires an admitted insurer to deny a workers' compensation claim within 90 days of the date the claim form is filed. If they don't, the claim is presumed compensable. That 90-day window creates operational pressure that shapes every AOE/COE investigation in California, and comparable good-faith rules apply across other western states.

What the 90-Day Rule Actually Says

Labor Code 5402(b) states: "If liability is not rejected within 90 days after the date the claim form is filed...the injury shall be presumed compensable." The presumption is rebuttable only by evidence that could not have been reasonably discovered earlier.

In plain terms: if the carrier wants to deny, the denial must go out within 90 days. The investigation supporting denial must be largely complete by then. A denial issued on day 92 with everything-but-one-witness is a problem.

Good-Faith Investigation

The 90-day rule presupposes a good-faith investigation. "Good faith" in this context means:

• Investigation is reasonably prompt
• Investigation is reasonably thorough
• The investigator actually pursued the evidence available
• The carrier made a reasoned decision based on the investigation

Good faith is not a numerical standard, but it is reviewable. Denials that rest on investigations that didn't actually happen get reversed at the WCAB and elsewhere.

What This Means for Investigation Scheduling

Running a full AOE/COE investigation inside 90 days requires pipeline discipline:

• Days 1-14: Intake and scoping. Recorded statement scheduled and taken. Employer interviews completed. Initial document requests.
• Days 14-30: Scene investigation (where applicable). Witness canvass. Social media investigation. ISO ClaimSearch and prior-claims research.
• Days 30-60: Medical canvass (HIPAA-authorized). Follow-up interviews. Any surveillance needed.
• Days 60-80: Analysis, AOE/COE report drafting, review by defense counsel.
• Days 80-90: Carrier decision and denial letter (if applicable), with final documentation.

Files that sit unassigned for weeks in the early window are files that miss the 90-day mark.

Delay and Deny Risk

"Delay and deny" means issuing a denial on day 89 after a superficial investigation. It's a high-risk posture. WCAB review of delay-and-deny patterns can result in:

• Reversal of the denial
• Penalty and attorney fee exposure under Labor Code 5814
• Referral of bad-faith claims handling to the DOI

A proper good-faith investigation inside 90 days is cheaper and safer than a thin denial that gets reversed.

Claim Denials Supported by the Investigation

Where the investigation produces a defensible basis for denial, the denial should:

• Identify the specific legal or factual ground
• Reference the investigation record
• Issue inside the 90-day window
• Preserve the insurer's right to rebut the presumption

Our AOE/COE investigation process post covers the investigation workflow that supports defensible denials.

Acceptance and Continuing Investigation

Not every accepted claim should have its investigation stop at acceptance. Many claims are accepted on limited information and then require ongoing investigation:

• Apportionment development as medical evaluation progresses
• Fraud investigation if red flags emerge post-acceptance
• Surveillance as reserves grow
• Return-to-work disputes that arise during treatment

See our surveillance when-to-order post for timing considerations.

Other States' Good-Faith Rules

The California 90-day rule is specific to California. Most other states have comparable good-faith investigation requirements:

• Nevada: statutory investigation timelines under NRS 616
• Arizona, Oregon, Idaho, Utah, Florida: each has its own framework

Carriers and TPAs operating across states need investigation vendors who know the jurisdictional rules and can run parallel workflows on the right schedule.

Operational Implications for Carriers

The 90-day rule, and its cousins elsewhere, means:

• Rapid referral to investigation is critical. A claim that sits on the adjuster's desk for 30 days before being referred has lost a third of the window.
• Concurrent workflows. Recorded statements, scene investigation, prior-claims research, and medical canvass should run in parallel, not serially.
• Consistent reporting format so adjusters can make timely decisions on investigation findings.
• Investigation vendor responsiveness. A vendor that doesn't start work promptly is a vendor that won't meet the window.

Our Approach

Our AOE/COE and workers' compensation services are built around the 90-day discipline. We accept referrals directly into an intake process, scope quickly, and run investigative work streams in parallel. We deliver reports formatted for carrier decision inside the window. For referrals on files approaching the window, we prioritize workflow and deliver core findings on a rapid basis.

This post is general information on the 90-day rule and good-faith investigation. Specific cases require counsel admitted in the applicable jurisdiction.