CA Lab Code Section 4625

(a)

Notwithstanding subdivision (d) of Section 4628, all charges for medical-legal expenses for which the employer is liable that are not in excess of those set forth in the official medical-legal fee schedule adopted pursuant to Section 5307.6 shall be paid promptly pursuant to Section 4622.

(b)

If the employer contests the reasonableness of the charges it has paid, the employer may file a petition with the appeals board to obtain reimbursement of the charges from the physician that are considered to be unreasonable.