Cal. Business and Professions Code § 2538.28

(a) An applicant who has fulfilled the requirements of Section 2538.24, and has made application therefor, and who proves to the satisfaction of the board that they will be supervised and trained by a hearing aid dispenser who is approved by the board may have a trainee license issued to them. The trainee license shall entitle the trainee licensee to fit or sell hearing aids as set forth in regulations of the board. The supervising dispenser shall be responsible for any acts or omissions committed by a trainee licensee under their supervision that may constitute a violation of this chapter. (b) The board shall adopt regulations setting forth criteria for its refusal to approve a hearing aid dispenser to supervise a trainee licensee, including procedures to appeal that decision. (c) A trainee license issued pursuant to this section is effective and valid for six months from date of issue. The board may renew the trainee license for an additional period of six months. Except as provided in subdivision (d), the board shall not issue more than two renewals of a trainee license to any applicant. Notwithstanding subdivision (d), if a trainee licensee who is entitled to renew a trainee license does not renew the trainee license and applies for a new trainee license at a later time, the new trainee license shall only be issued and renewed subject to the limitations set forth in this subdivision. (d) A new trainee license may be issued pursuant to this section if a trainee license issued pursuant to subdivision (c) has lapsed for a minimum of three years from the expiration or cancellation date of the previous trainee license. The board may issue only one new trainee license under this subdivision.