§ 172.110.Supplement or Amendment to Statement

Amendment is the default, with two ways to stop it.

A party may amend or supplement a claim or defense during the arbitration. No leave is required as a starting point.

The parties may agree otherwise, and institutional rules sometimes impose a cut-off.

The tribunal may refuse. It may consider the amendment inappropriate considering the delay in making it.

Delay is the stated criterion. The section does not speak of prejudice or of the merits of the amendment, but of when it was offered.

The liberal default suits an evolving record. International cases develop as documents are exchanged and experts report, and a rigid pleading rule would force parties to plead defensively at the start.

The tribunal’s discretion is the counterweight. An amendment sprung late can force a postponement and additional cost, and the tribunal that will bear the schedule decides.

Equal treatment still applies. Section 172.101 requires a full opportunity to present a case, and a party facing a late amendment must have a chance to answer it.

An amended claim can affect the award. Section 172.148 allows an additional award for a claim presented but omitted, which presupposes the claims before the tribunal.