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Bao Ha Cong Anh and Quang Anh Nguyen address whether a respondent’s late counterclaim may be admitted in commercial arbitration after the claimant has materially amended its case. They locate the question in the procedural asymmetry that arises when claimants can reshape the dispute while respondents remain subject to deadlines set by reference to the original claims, considering the parties’ existing consent to arbitration and procedural equality.
The authors argue that a material amendment does not automatically create a right to counterclaim, but may justify consideration of a genuinely responsive counterclaim within the existing consent to arbitration. Drawing on comparisons of the UNCITRAL, ICC, SIAC and LCIA frameworks, their Structured Admissibility Test considers jurisdiction and consent, the causal justification for delay, respondent diligence and whether prejudice can be cured through proportionate timetable or cost measures.
Whether a counterclaim submitted after the claimant materially amends its case may be admitted consistently with the parties’ existing consent to arbitration and procedural equality.
The article frames the relationship between a material amendment to the claimant’s case and the respondent’s opportunity to bring a counterclaim through consent to arbitration, procedural equality and concrete prejudice, rather than an automatic entitlement or an inflexible time-bar. It therefore identifies criteria for more consistent exercises of arbitral discretion over late counterclaims.
Journal of International Arbitration · 2026
DOI 10.54648/joia2026025