Quick Tips: The 90-Day Investigation Period in California Workers’ Compensation

When an employee reports a workplace injury in California, the first 90 days after notice of the claim can significantly impact how the case develops. This period—commonly called the investigation period under Labor Code § 5402—is when the employer and claims administrator determine whether the injury is compensable under the workers’ compensation system. Because California workers’ compensation is a no-fault system, early documentation and investigation are essential to managing exposure, litigation posture, and long-term claim costs.

When the Investigation Period Begins

The investigation period begins when the employer either receives knowledge of an injury or receives a completed DWC-1 claim form. California law requires employers to provide the injured worker with the DWC-1 within one working day of learning about the injury. Once the claim form is received, the claims administrator has 14 days to accept the claim, deny the claim, or delay the claim pending investigation.

If the claim is delayed, the employer has up to 90 days from the date of notice to complete the investigation and issue a denial. If no denial is issued within those 90 days, the claim is presumed compensable, making it significantly more difficult to dispute the claim later unless new evidence emerges that could not reasonably have been discovered earlier.

What Happens During a Delay

A delay allows time to gather information before deciding whether the claim should be accepted or denied. During this investigation period, the employer must authorize up to $10,000 in medical treatment for the injured worker. However, issuing a delay does not mean the claim has been accepted; it simply allows the claims administrator to conduct a proper investigation into the circumstances of the injury.

Key Areas to Evaluate During the Investigation

A thorough investigation focuses on several core areas that can help determine whether the injury arose out of and occurred in the course of employment (AOE/COE).

Timing issues often provide important clues. Claims reported long after the alleged injury, or claims filed immediately after disciplinary action, termination, or layoffs, may warrant additional scrutiny.

Mechanism of injury should also be evaluated. If the alleged injury is inconsistent with the employee’s job duties or if the description of the event changes over time, these inconsistencies may impact the credibility of the claim.

Medical history is another critical component. Prior injuries to the same body part, inconsistent reporting to medical providers, or evidence of non-industrial causes such as sports activities or motor vehicle accidents may affect the compensability analysis.

Employment and personnel records can also provide key evidence. Attendance records, disciplinary files, job descriptions, and wage records often help determine whether the reported injury is consistent with the employee’s work duties and help calculate potential disability exposure.

How Employers Can Assist the Investigation

Employers play a crucial role in helping adjusters and defense counsel conduct an effective investigation. Immediate documentation and early evidence preservation can significantly strengthen the defense of a claim. Supervisor incident reports, written witness statements, and preserved video footage can provide valuable information about how the injury allegedly occurred.

Employers should also provide accurate job descriptions, wage records, and personnel files so the claims administrator has a complete understanding of the employee’s duties and employment history. Early communication with the adjuster and defense counsel allows potential credibility issues or red flags to be addressed quickly.

Strategic Impact: Accepting vs. Denying the Claim

The decision to accept or deny a claim has significant strategic implications. If a claim is accepted, the employer becomes responsible for reasonable and necessary medical treatment and potential disability benefits, and disputing industrial causation later becomes more difficult.

If the claim is denied, the injured worker may retain counsel and pursue litigation before the Workers’ Compensation Appeals Board. In that scenario, medical-legal evaluations often become central to determining whether the injury is industrial. If a denial is overturned, liability may apply retroactively, and penalties may be assessed if the denial was unreasonable.

Why the First 90 Days Matter

The investigation period is often the most important phase of a workers’ compensation claim. The information gathered during these first 90 days can determine whether liability can be avoided entirely, whether the case can be resolved early, or whether it will proceed into extended litigation.

Employers who respond quickly, document carefully, and communicate early with claims administrators and defense counsel place themselves in the strongest position to control costs and achieve favorable outcomes in workers’ compensation cases.