California Code, Code of Civil Procedure - CCP § 116.360

(a) The defendant may file a claim against the plaintiff in the same action in an amount not to exceed the jurisdictional limits stated in Sections 116.220, 116.221, and 116.231. The claim need not relate to the same subject or event as the plaintiff's claim.

(b) The defendant's claim shall be filed and served in the manner provided for filing and serving a claim of the plaintiff under Sections 116.330 and 116.340.

(c) The defendant shall cause a copy of the claim and order to be served on the plaintiff at least five days before the hearing date, unless the defendant was served 10 days or less before the hearing date, in which event the defendant shall cause a copy of the defendant's claim and order to be served on the plaintiff at least one day before the hearing date.