Cal. Gov't Code § 84105

(a) A candidate or committee that receives contributions totaling five thousand dollars ($5,000) or more from a person in a calendar year shall inform that contributor within two weeks of receipt that the contributor may be required to file campaign reports. The notice shall include a reference to the filing requirements for multipurpose organizations under Section 84222.
(b) A candidate or committee that receives a contribution of ten thousand dollars ($10,000) or more from a person during a period in which late-contribution reports are required to be filed under Section 84203 shall provide the information in subdivision (a) of that section to the contributor within one week.
(c) The notifications required by this section need not be sent to a contributor who has an identification number assigned by the Secretary of State issued under Section 84101.