Dont Let Apportionment Sink Your SIBTF Claim

Analysis by: Exam Specialists Medical Group; Patzy Fuentes  

Editorial review provided by Justin Sonnicksen, Esq.

A Common Mistake 

Imagine you represent an injured worker who, after a serious work injury, is left with a 60% impairment. You consider helping your client obtain SIBTF benefits, but because their injury was apportioned, the disability appears to fall below 35%, failing to meet the threshold to apply for SIBTF benefits. A common mistake is that many practitioners, and even some judges, mistakenly subtract prior injuries from this initial threshold, not realizing that subtracting from the initial threshold is not required under the law.

The Core Rule: “The Standing Principle” 

A recent panel decision of the WCAB, issued in October of 2025, titled Corrales v SIBTF, as summarized in the November 2025 edition of the California Workers' Compensation Reporter (CWCR), confirms that apportionment is not considered in calculating the 35% SIBTF requirement. The decision explains that the 35% threshold must be considered “standing alone”, meaning that  when calculating the initial 35% requirement, subtracting apportionment for non-industrial or prior industrial injuries is not required. 

To understand the math, consider for example a qualifying industrial injury that results in a 60% permanent impairment when the worker reaches MMI status, but 50% of the impairment is from a pre existing injury.  This methodology is consistent with the 1976 Court of Appeal decision in Bookout which held that the Labor Code 4751 requirement that “ ‘the permanent disability resulting from the subsequent injury, when considered alone without regard to or adjustment for the occupation or the age of the employee’ was also meant to exclude apportionment” (CWCR p. 191).  

As distinct as the 35% and 70% are in meeting their respective thresholds, a simple comparison helps clarify the two different “hurdles”. To reach the first threshold of 35% for SIBTF eligibility, there is no requirement for apportionment and no age and occupation adjustments taken into account. However, when determining the 70% total PD to reach SIBTF’s qualification for compensation, apportionment is applied here and the age and occupation adjustments are included to find the final combined PD rating.

CTA : Why This Matters 

Referring to the editors note in the CWCR case summary “Apportionment Not Considered in Calculating 35 Percent SIBTF Requirement”, it is important for an attorney to advocate for SIBTF benefits using the correct methodology. If the “standing alone” rule fails to be understood, it can result in the loss of fees for the attorney and more importantly, the loss of potential benefits for the injured worker. 

The Corrales decision provides a clear roadmap for workers who are eligible to secure SIBTF benefits, and holds that a worker with a significant history of prior injuries can still meet the 35% qualification threshold.

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