(a) Except as otherwise provided by statute, if a party against whom a complaint has been filed and served fails to allege in a cross-complaint any related cause of action which (at the time of serving his answer to the complaint) he has against the plaintiff, such party may not thereafter in any other action assert against the plaintiff the related cause of action not pleaded.
§ 426.30.Failure to Allege Related Cause of Action Against Plaintiff In Cross-Complaint
Title 6. Of the Pleadings In Civil Actions · Chapter 2. Pleadings Demanding Relief · Article 2. Compulsory Cross-Complaints · Enacted 1971 · no amendments on record · Last verified July 28, 2026
In one sentenceSection 426.30 requires a defendant who has a related cause of action against the plaintiff at the time of answering to plead it in a cross-complaint or lose the right to assert it in any later action, unless the court lacked jurisdiction to render a personal judgment against that party or the party never answered the complaint.
Full Text of § 426.30
(b) This section does not apply if either of the following are established:
(1) The court in which the action is pending does not have jurisdiction to render a personal judgment against the person who failed to plead the related cause of action.
(2) The person who failed to plead the related cause of action did not file an answer to the complaint against him.
Plain-English Summary
Section 426.30 is California's compulsory cross-complaint rule, and it carries real teeth. Subdivision (a) states the core requirement: if a party has been served with a complaint and, at the time of serving an answer to it, has a related cause of action (as defined in § 426.10) against the plaintiff, that party must allege it in a cross-complaint in the same action. Fail to do so, and that party cannot assert the related cause of action against the plaintiff in any other action later.
The rule is about efficiency and finality: once the parties are litigating a dispute arising from a shared transaction or occurrence, the law wants every related claim resolved in that one proceeding rather than spread across successive lawsuits. A defendant who sits on a related claim, intending to bring it separately later, risks losing it altogether.
Subdivision (b) narrows the rule with two exceptions. It does not apply if the court hearing the original action lacked jurisdiction to render a personal judgment against the party who failed to plead the related claim, and it does not apply if that party never filed an answer to the complaint in the first place — a defaulting defendant is not penalized under this section for failing to cross-complain. Because the loss of an unpleaded related claim is severe, § 426.50 provides a safety valve: a party who omitted the claim through oversight, inadvertence, mistake, or neglect, acting in good faith, can seek leave to amend and add it at any point during the same action, and courts are directed to construe that relief liberally to avoid forfeiture.
Frequently Asked Questions
What happens if I don't raise a related claim against the plaintiff in my answer?
Section 426.30(a) bars a party from later asserting that related cause of action against the plaintiff in any other action, if the party had it at the time of serving the answer and failed to plead it in a cross-complaint.
What counts as a 'related' cause of action for purposes of this rule?
Section 426.10(c) defines it as a cause of action arising out of the same transaction, occurrence, or series of transactions or occurrences as the plaintiff's own claim.
Are there exceptions to the compulsory cross-complaint rule?
Yes. Section 426.30(b) exempts a party from the rule if the court lacked jurisdiction to render a personal judgment against that party, or if the party never filed an answer to the complaint.
What if I forgot to plead a related claim by mistake — is it lost forever?
Not necessarily. Section 426.50 lets a party who omitted a related cause of action through oversight, inadvertence, mistake, or neglect, acting in good faith, apply for leave to amend or file a cross-complaint asserting it at any time during the action, and directs courts to construe that relief liberally.
Does the compulsory cross-complaint rule apply to every kind of case?
No. Section 426.40 narrows it further where additional required parties are outside the court's jurisdiction, where the claim is constitutionally or statutorily barred from that court and any transferee court, or where the claim was already the subject of another pending action when the current action was commenced. Section 426.60 also excludes special proceedings, small claims actions, and actions seeking only declaratory relief.
Amendment History
Added by Stats. 1971, Ch. 244.
Source & verification. Section text is reproduced verbatim from
the Deering's California Codes Annotated / vLex. Enacted by the California Legislature.
Last verified July 28, 2026.
· Official source
Also known as: compulsory cross complaint californiause it or lose it cross complaint rulecalifornia cross complaint requirementfailure to file cross complaint california consequences