Cal. Lab. Code § 5501
The application may be filed with the appeals board by any party in interest, his attorney, or other representative authorized in writing. A representative who is not an attorney licensed by the State Bar of this state shall notify the appeals board in writing that he or she is not an attorney licensed by the State Bar of this state. Upon the filing of the application, the appeals board shall, where the applicant is represented by an attorney or other representative, serve a conformed copy of the application showing the date of filing and the case number upon applicant's attorney or representative. The applicant's attorney or representative shall, upon receipt of the conformed copy, forthwith serve a copy of the conformed application upon all other parties to the claim. If the applicant is unrepresented, a copy thereof shall forthwith be served upon all adverse parties by the appeals board.
Ca. Lab. Code § 5501