Cal. Civil Code §3098
“Preliminary 20-day notice (public work)” means a written notice from a claimant that was given prior to the assertion of a claim against a payment bond, or the filing of a stop notice on public work, and is required to be given under the following circumstances:
(a)In any case in which the law of this state affords a right to a person furnishing labor or materials for a public work who has not been paid therefor to assert a claim against a payment bond, or to file a stop notice with the public agency concerned, and thereby cause the withholding of payment from the contractor for the public work, any person that has no direct contractual relationship with the contractor, other than a person who performed actual labor for wages or an express trust fund described in Section 3111, may file the preliminary notice, but no payment shall be withheld from the contractor pursuant to that notice unless the person has caused written notice to be given to the contractor, and the public agency concerned, not later than 20 days after the claimant has first furnished labor, services, equipment, or materials to the jobsite, stating with substantial accuracy a general description of labor, service, equipment, or materials furnished or to be furnished, and the name of the party to whom the same was furnished. This notice shall be served by mailing the same by first-class mail, registered mail, or certified mail, postage prepaid, in an envelope addressed to the contractor at any place the contractor maintains an office or conducts business, or his or her residence, or by personal service. In case of any public works constructed by the Department of Public Works or the Department of General Services of the state, such notice shall be served by mailing in the same manner as above, addressed to the office of the disbursing officer of the department constructing the work, or by personal service upon the officer. When service is by registered or certified mail, service is complete at the time of the deposit of the registered or certified mail.
(b)Where the contract price to be paid to any subcontractor on a particular work of improvement exceeds four hundred dollars ($400), the failure of that contractor, licensed under Chapter 9, (commencing with Section 7000) of Division 3 of the Business and Professions Code, to give the notice provided for in this section, constitutes grounds for disciplinary action by the Registrar of Contractors.
(c)The notice requirements of this section shall not apply to a laborer described in Section 3089 or to an express trust fund described in Section 3111.
(d)If labor, service, equipment, or materials have been furnished to a jobsite by a claimant who did not give a preliminary notice pursuant to subdivision (a), that claimant shall not be precluded from giving a preliminary notice at any time thereafter. The claimant shall, however, be entitled to assert a claim against a payment bond and file a stop notice only for labor, service, equipment, or material furnished within 20 days prior to the service of the preliminary notice, and at any time thereafter.
(e)The failure to provide, pursuant to Chapter 974 of the Statutes of 1994, a written preliminary notice to a subcontractor with whom the claimant has contracted shall not affect the validity of any preliminary notice provided pursuant to this section.