Unless otherwise agreed by the parties, either party may amend or supplement his or her claim or defense during the course of the arbitral proceedings, unless the arbitral tribunal considers it inappropriate to allow the amendment or supplement having regard to the delay in making it.
§ 1297.233.Amendment Or Supplementation of Claim Or Defense
Title 9.3. Arbitration and Conciliation of International Commercial Disputes · Chapter 5. Manner and Conduct of Arbitration · Article 6. Statements of Claim and Defense · Enacted 1988 · no amendments on record · Last verified July 29, 2026
In one sentenceSection 1297.233 allows either party to amend or supplement its claim or defense as the arbitration proceeds, unless the parties agreed otherwise or the tribunal decides the amendment comes too late to be fair to allow.
Full Text of § 1297.233
Plain-English Summary
Disputes rarely look the same at the end as they did at the start, and this section lets the pleadings catch up. Either party may amend or supplement its claim or defense during the arbitral proceedings, picking up facts or theories that weren't apparent when the original statement went in.
That flexibility has a limit built in. The tribunal may refuse to allow an amendment or supplement if it considers doing so inappropriate given the delay in making it. A party that waits too long, especially close to a hearing, risks losing the chance to add a new claim or defense, since the tribunal weighs the disruption to the other side against the value of letting the case reflect what the parties are truly arguing.
Frequently Asked Questions
Can a party change its claim or defense after the arbitration has started?
Yes, unless the parties have agreed otherwise. Either party may amend or supplement its claim or defense during the arbitral proceedings.
Is there any limit on making these changes?
Yes. The arbitral tribunal may refuse an amendment or supplement if it considers it inappropriate given the delay in making it.
What kind of delay might lead a tribunal to reject an amendment?
The section doesn't list specific examples, but a request made late enough to disrupt the hearing schedule or prejudice the other party's preparation is the kind of delay the tribunal weighs.
Amendment History
Added by Stats. 1988, Ch. 23, Sec. 1. Effective March 7, 1988.
Source & verification. Section text is reproduced verbatim from
the Deering's California Codes Annotated / vLex. Enacted by the California Legislature.
Last verified July 29, 2026.
· Official source
Also known as: amending arbitration claim or defensesupplementing pleadings international arbitration