What has changed and what does it mean for experts?

On June 1, 2026, the International Chamber of Commerce (ICC) launched its new Rules of Arbitration¹. This is not a cosmetic revision. It is the most substantive update since 2021,² described by the ICC as intended to ‘enhance efficiency, clarity, and usability,’³ and can be seen, in part, as a response to feedback that has been building for years: international arbitration has become too slow and too expensive.

The context matters. In 2025, the ICC administered 881 new cases with an aggregate of approximately USD 41 billion, and ended the year with a record pending caseload valued at USD 299 billion⁴. It is one of the most widely used arbitral forums in the world, and when it changes its rules, the effects are felt immediately: in contracts, in procedural strategies, and in how experts work.

The more specific question is: what do these changes mean for experts who participate in ICC arbitrations?   

The ICC made several adjustments in its new Rules, but five of them genuinely shift the dynamics for an expert:

1. The Highly Expedited Arbitration Provisions (HEAP): A Final Award in Three Months

This is the most disruptive change. HEAP⁵ is an opt-in mechanism that allows parties to obtain a final award within approximately three months from the initial Case Management Conference (CMC). To meet that timeline, the full statement of claim, with arguments, facts, and supporting evidence, must be filed together with the Request for Arbitration, not afterward.

Three months is a short window in any arbitration. In a case with technically complex components, quantum analysis, causation, delay, or financial modelling, it forces a fundamental rethink of how the expert's work is structured.

2. The Expedited Procedure Threshold Rises to USD Four Million

Previously set at USD three million, the threshold increases to USD four million for arbitration agreements signed on or after June 1, 2026⁶. Notably, over 40% of ICC cases in 2025 did not exceed that amount⁷, meaning a large portion of arbitrations will fall under compressed timelines by default unless the parties agree otherwise.

3. The Terms of Reference Are No Longer Mandatory

The Terms of Reference had been a defining feature of ICC arbitration for decades. They set out the scope of the dispute, identify the claims, and establish a formal procedural framework before the arbitration progresses. As of June 2026, they are no longer mandatory⁸. The extent to which tribunals will dispense with terms of reference remains to be seen.

The key procedural milestone is now the initial CMC, which must take place within 30 days of the tribunal receiving the file⁹. Critically, after the CMC, no new claims may be introduced without the tribunal's authorization¹⁰. This means the scope of the case becomes fixed much earlier than before.

4. Greater Flexibility in Communications and Hearings

The new Rules formalize electronic communications as the norm for written communications. They now expressly allow hybrid (not previously mentioned in the 2021 rules), as well as videoconference or teleconference hearings, and expressly allow the same for arbitral deliberations (which was less clear before) and electronic signing of awards. On paper, this is not a dramatic shift, but it codifies what the pandemic accelerated and what many arbitral tribunals were already doing in practice.

5. Stronger Disclosure Obligations: Arbitrators and Third-Party Funders

The independence and impartiality requirements for arbitrators have tightened¹¹. The rules are now explicit: where there is any doubt about whether information should be disclosed, that doubt is resolved in favor of disclosure. Parties must also submit, when filing a Request, an Answer, a Request for Joinder, an Answer to a Request for Joinder, or a request for an extension of time to submit an Answer, a list of persons and entities that they believe prospective arbitrators and arbitrators should consider. There is also a specific requirement for parties to promptly inform the Secretariat, the arbitration tribunal, and the other parties of the existence of any non-party that has entered into an arrangement to fund claims or defenses. As an arbitrator’s links to an expert have themselves been a source of challenge, this stronger pro-disclosure default is likely to affect experts as well.

Each of these changes touches, in one way or another, on how the expert works. 

• The 2026 Rules do a good deal to speed the process, but they stop short of addressing some of the largest sources of delay and cost in expert evidence. Some measures may not sit naturally in a rulebook; even so, tribunals can address them under existing case management powers, for example, in Procedural Order No. 1:
• Aligning the basis of expert calculations. Opposing experts frequently calculate using different legal, factual, or methodological bases and assumptions. A tribunal can direct each side’s expert to calculate using the other side’s approach as well as its own, with appropriate methodologies and key assumptions settled early in case management and reports prepared on that basis. Experts will not always agree on methodology, but often the difference is not a real dispute and remains unaddressed. Doing this properly requires tribunals to engage with expert evidence far earlier than they typically do.
• Sequence quantum earlier where appropriate. Tribunals customarily proceed in the order: jurisdiction, merits, then quantum. In suitable cases, a tribunal can consider whether hearing quantum earlier would assist, for example, where the difference between the parties’ quantum figures is narrow, or where one side’s quantum case is clearly unsustainable. Surfacing damages issues sooner may promote settlement or early disposition of the case.
• Greater use of hot-tubbing and witness conferencing. Used with proper tribunal preparation, which a tribunal appointed expert can support (see below), concurrent expert evidence can be far more efficient than sequential examination.
• Deconstruct expert valuations, particularly DCF. Greater teaching and use of methods to break down complex valuations would help. For example, this could mean requiring the key assumptions and the key logic of a calculation to be set in a form that the tribunal can readily follow, such as flow charts or hierarchies, versus Excel or in equations.
• Use tribunal-appointed experts in appropriate cases. To meet the ‘fourth arbitrator’ concern, this need not take the form of a full expert report. A tribunal-appointed expert could instead be used to (i) help the tribunal frame questions to ask in hot-tubbing; (ii) identify where the parties’ reports are not on the same basis and how they might be aligned; and (iii) explain to the tribunal the key assumptions and logic behind a figure where these have not been made clear.

The ICC 2026 Rules do not change what makes arbitration a strong mechanism for resolving complex disputes, but they do change the pace at which it unfolds. In faster proceedings, the experts who are well-prepared from the outset have more influence, not less.

The critical question is not whether these changes affect the work, but whether teams are organized to meet the new pace. Those that are ready will have an edge.

References

[1] “2026 Arbitration Rules,” International Chamber of Commerce (ICC), June 1, 2026.

[2] “The 2026 ICC Arbitration Rules: A Practical Guide for Counsel to the Most Significant Overhaul in a Decade,” Kluwer Arbitration Blog, June 8, 2026.

[3] “New ICC Rules of Arbitration enhance efficiency, clarity and usability,” International Chamber of Commerce (ICC), May 22, 2026.

[4] “The 2026 ICC Arbitration Rules: Key Reforms for Energy and Maritime Counsel,” Haynes Boone, June 16, 2026. 

[5] “ICC Arbitration Rules Effective June 1, 2026: Key Changes and Practical Takeaways for Parties and Counsel,” citing Art. 33, Goodwin, June 1, 2026. 

[6] “The 2026 ICC Arbitration Rules: Key Reforms for Energy and Maritime Counsel,” citing appendix V, Art. 1, Haynes Boone, June 16, 2026.

[7] “Unveiling the 2026 ICC Arbitration Rules, Part 3: Expedited Procedure Provisions and Emergency Arbitration,” International Chamber of Commerce (ICC), May 19, 2026.

[8] “The 2026 ICC Arbitration Rules: Summary of Key Updates,” Norton Rose Fulbright, May 2026. 

[9] “ICC Releases New 2026 Arbitration Rules: Key Changes Effective 1 June 2026,” citing Art. 24(1),Crowell & Moring LLP, June 3, 2026. 

[10] “Key Changes in the 2026 ICC Arbitration Rules,” citing Art. 25, Aceris Law LLC, May 30, 2026. 

[11] “ICC Arbitration Rules 2026: Key Changes and Legal Analysis,” op. cit., citing Art. 12, CMS, May 29, 2026.