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IMEPro
Impairment Rating
Updated March 2026

Apportionment

Legal basis: LC §4663

Definition

The process of determining what percentage of a worker's permanent disability is caused by the industrial injury versus pre-existing conditions, prior injuries, or non-industrial factors. Under California law, the employer is only liable for the portion of disability directly caused by the work-related injury.

Key Facts About Apportionment in 2026

QME Physicians in CA

~2,500

Evaluation Fee Range

$2,500-$4,000

Report Deadline

30 days

Avg AI-Assisted Turnaround

14 days

Related Terms

Frequently Asked Questions

What is a Apportionment?

The process of determining what percentage of a worker's permanent disability is caused by the industrial injury versus pre-existing conditions, prior injuries, or non-industrial factors. Under California law, the employer is only liable for the portion of disability directly caused by the work-related injury.

What is the legal basis for Apportionment in California workers' compensation?

Apportionment is governed by LC §4663 under California workers' compensation law. This statute defines the requirements, procedures, and standards for apportionment in the workers' compensation system as of 2026.

How is apportionment calculated in California?

Apportionment in California workers' compensation is typically determined using the AMA Guides to the Evaluation of Permanent Impairment, 5th Edition (2001). QME and AME physicians use standardized rating methods to ensure consistency across evaluations.