California Code, Government Code - GOV § 84303

(a) An expenditure of five hundred dollars ($500) or more shall not be made, other than for overhead or normal operating expenses, by an agent or independent contractor, including, but not limited to, an advertising agency, on behalf of or for the benefit of a candidate or committee unless it is reported by the candidate or committee as if the expenditure were made directly by the candidate or committee.

(b) A subagent or subcontractor who provides goods or services to or for the benefit of a candidate or committee shall make known to the agent or independent contractor all of the information required to be reported by this section, and the agent or independent contractor shall then make known to the candidate or committee all of the information required to be reported by this section no later than three working days prior to the time the campaign statement reporting the expenditure is required to be filed, except that an expenditure that is required to be reported by Section 84203 or 84204 shall be reported to the candidate or committee within 24 hours of the time that it is made.