Cal. Labor Code § 3302

(a) (1) When a licensed contractor enters an agreement with a temporary employment agency, employment referral service, labor contractor, or other similar entity for the entity to supply the contractor with an individual to perform acts or contracts for which the contractor’s license is required under Chapter 9 (commencing with Section 7000) of Division 3 of the Business and Professions Code and the licensed contractor is responsible for supervising the employee’s work, the temporary employment agency, employment referral service, labor contractor, or other similar entity shall pay workers’ compensation premiums based on the contractor’s experience modification rating. (2) The temporary employment agency, employment referral service, labor contractor, or other similar entity described in paragraph (1) shall report to the insurer both of the following: (A) Its payroll on a monthly basis in sufficient detail to allow the insurer to determine the number of workers provided and the wages paid to these workers during the period the workers were supplied to the licensed contractor. (B) The licensed contractor’s name, address, and experience modification factor as reported by the licensed contractor. (C) The workers’ compensation classifications associated with the payroll reported pursuant to subparagraph (A). Classifications shall be assigned in accordance with the rules set forth in the California Workers’ Compensation Uniform Statistical Reporting Plan published by the Workers’ Compensation Insurance Rating Bureau. (b) The temporary employment agency, employment referral service, labor contractor, or other similar entity supplying the individual under the conditions specified in subdivision (a) shall be solely responsible for the individual’s workers’ compensation, as specified in subdivision (a). (c) Nothing in this section is intended to change existing law in effect on December 31, 2002, as it relates to the sole remedy provisions of this division and the special employer provisions of Section 11663 of the Insurance Code. (d) A licensed contractor that is using a temporary worker supplied pursuant to subdivision (a) shall notify the temporary employment agency, employment referral service, labor contractor, or other similar entity that supplied that temporary worker when either of the following occurs: (1) The temporary worker is being used on a public works project. (2) The contractor reassigns a temporary worker to a position other than the classification to which the worker was originally assigned. (e) A temporary employment agency, employment referral service, labor contractor, or other similar entity may pass through to a licensed contractor any additional costs incurred as a result of this section.