Cal. Rev. & Tax. Code § 41119

In any action brought under this part, process may be served according to the Code of Civil Procedure and the Civil Code of this state or may be served upon any agent or clerk in this state employed by a service supplier or seller in a place of business maintained by the service supplier or seller in this state. In the latter case a copy of the process shall forthwith be sent by registered mail to the service supplier or seller at its principal or home office.