International Arbitration Terms: An Expert’s Quick Guide — Harberry
International arbitration has a vocabulary of its own. And the same step can go by several names, depending on the rules, the institution and, often, the background of counsel.
A Statement of Claim in one case is a Memorial in another. A ‘rebuttal’ expert report in one is a ‘reply’ report in the next. None of them is wrong; they are simply different conventions for the same thing.
For an expert witness, the names matter. A report should carry the title the tribunal’s Procedural Order gives it, and it helps to know where it sits in the overall sequence. So I have put together a one-page quick guide to the terms commonly used in international arbitration, stage by stage, from the Notice of Arbitration to the Award. It reflects the rules as at October 2026, including the 2026 ICC Arbitration Rules.
Download the quick guide (PDF, one page)
What are the stages of an arbitration?
Common names shown in the third column. The applicable rules and the tribunal’s Procedural Order govern the names used in any given case.
Memorial or Statement of Claim? The written submissions
Reply and Rejoinder are the parties’ submissions; ‘rebuttal’ usually describes the evidence served with them.
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RoundPartyCommercial arbitration nameICSID / investment nameEvidence commonly served with it
Rebuttal, reply or supplementary? The expert reports
Any further expert report is exceptional and subject to the tribunal’s directions, usually confined to specified new matters or developments.
So which name is right?
Simplistically, the one in the Procedural Order. Terminology varies between institutions, between cases and sometimes within the same case, so the tribunal’s directions are the place to check. The guide is a map of the names you are likely to hear, not a rule book.
Frequently asked questions
What is the difference between a Memorial and a Statement of Claim?
Both are the claimant’s first main written submission. ‘Memorial’ is used in ICSID and many investment treaty cases; ‘Statement of Claim’ is the more common term in commercial arbitration.
What is a Rejoinder?
The respondent’s second-round written submission, answering the claimant’s Reply.
Can there be a third expert report?
Only if the tribunal permits it. Any further report is exceptional and is usually confined to specified new matters or developments.
Download the quick guide (PDF, one page)
For general information only; not legal advice. Terminology varies between institutions and cases: the applicable rules and the tribunal’s Procedural Order govern. Rules as at October 2026: UNCITRAL Arbitration Rules (2013); ICC Arbitration Rules (2026; the 2021 Rules may apply to earlier proceedings); LCIA Arbitration Rules (2020); ICSID Arbitration Rules (2022); IBA Rules on the Taking of Evidence in International Arbitration (2020). Version 1.1, October 2026. Prepared by Andrew White, Harberry&Co., with AI assistance (Claude, Anthropic).
Originally published at https://harberry.com on October 17, 2026.
