Cal. Lab. Code § 226.4

If, upon inspection or investigation, the Labor Commissioner determines that an employer is in violation of subdivision (a) of Section 226, the Labor Commissioner may issue a citation to the person in violation. The citation may be served personally or by registered mail in accordance with subdivision (c) of Section 11505 of the Government Code. Each citation shall be in writing and shall describe the nature of the violation, including reference to the statutory provision alleged to have been violated.