California Code, Business and Professions Code - BPC § 2538.34

(a) Every licensee who engages in the practice of fitting or selling hearing aids shall have and maintain an established retail business address to engage in that fitting or selling, routinely open for service to customers or clients. The address of the licensee's place of business shall be registered with the board as provided in Section 2538.33.

(b) Except as provided in subdivision (c), if a licensee maintains more than one place of business within this state, he or she shall apply for and procure a duplicate license for each branch office maintained. The application shall state the name of the person and the location of the place or places of business for which the duplicate license is desired.

(c) A hearing aid dispenser may, without obtaining a duplicate license for a branch office, engage on a temporary basis in the practice of fitting or selling hearing aids at the primary or branch location of another licensee's business or at a location or facility that he or she may use on a temporary basis, provided that the hearing aid dispenser notifies the board in advance in writing of the dates and addresses of those businesses, locations, or facilities at which he or she will engage in the practice of fitting or selling hearing aids.