California Code, Code of Civil Procedure - CCP § 116.560

(a) Whenever a claim that is filed against a person operating or doing business under a fictitious business name relates to the defendant's business, the court shall inquire at the time of the hearing into the defendant's correct legal name and the name or names under which the defendant does business. If the correct legal name of the defendant, or the name actually used by the defendant, is other than the name stated on the claim, the court shall amend the claim to state the correct legal name of the defendant, and the name or names actually used by the defendant.

(b) The plaintiff may request the court at any time, whether before or after judgment, to amend the plaintiff's claim or judgment to include both the correct legal name and the name or names actually used by the defendant. Upon a showing of good cause, the court shall amend the claim or judgment to state the correct legal name of the defendant, and the name or names actually used by the defendant.

(c) For purposes of this section, “fictitious business name” means the term as defined in Section 17900 of the Business and Professions Code.