California Code, Business and Professions Code - BPC § 6408

The registrant's name, business address, telephone number, registration number, and county of registration shall appear in any solicitation or advertisement, and on any printed papers or documents prepared or used by the registrant, including, but not limited to, contracts, letterhead, business cards, correspondence, documents, forms, claims, petitions, checks, receipts, and pleadings.The registrant's name, business address, telephone number, registration number, expiration date of the registration, and county of registration shall appear on the written contract required to be provided to a client pursuant to Section 6410, as well as on any Internet Web site maintained by the registrant, and in any solicitation, advertisement, document, or correspondence prepared or used by the registrant in electronic form.