Cal. Bus. & Prof. Code § 6408

The registrant’s name, business address, telephone number, registration number, expiration date of the registration, and county of registration shall appear in any solicitation or advertisement, and on any 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, money orders, and pleadings.