Challenging an Arbitral Award? The English Commercial Court’s latest reminder on timing

The English courts have consistently enforced the strict time limits in the Arbitration Act 1996 (the “1996 Act”) for challenging arbitral awards, reflecting a strong commitment to the principle of finality.  A recent Commercial Court decision confirms that this commitment extends beyond the commencement of a challenge: a party cannot assume that filing a challenge within time will preserve its ability to expand the challenge later.

In E v F [2026] EWHC 1493 (Comm), the Commercial Court (Mr Justice Robin Knowles CBE) refused a State’s application to broaden its section 67 (substantive jurisdiction) and section 68 (serious irregularity) challenge to an award rendered in an investment-treaty arbitration. Although the State had commenced its challenge in time, the proposed amendments were advanced 162 days after the award, more than five times the 28-day statutory limit. 

The decision is a useful illustration of the weight the English courts continue to place on the finality of arbitral awards. It also serves as a reminder that a party wishing to challenge an award should seek to formulate the grounds for doing so fully and within the statutory time limit. Late attempts to expand the challenge may be rejected even where there is no obvious prejudice to the respondent party. 

Background

The dispute arose out of an award dated 31 July 2025 (the “Award”) made under a Bilateral Investment Treaty and the UNCITRAL Rules 1976. By a majority, the tribunal found that it had jurisdiction in the dispute between the claimants (“F”) and the respondent State, and required the State to pay compensation to F.

On 27 August 2025 (i.e. within the statutory time limit of 28 days from the date of the Award), the State commenced a claim in the Commercial Court challenging the tribunal’s jurisdiction under section 67 of the 1996 Act and alleging serious irregularity affecting the Award under section 68. On 9 January 2026, the State applied to amend its claim. Certain amendments opposed by F fell to be determined by the Court. 

The legal framework

Section 70(3) of the 1996 Act imposes a 28-day time limit for a challenge to an award, with the applicable date for the commencement of that time limit being the date of the award in this case.  Section 80(5) permits the Court to extend that period on application. The Court emphasised the foundational principle in section 1 of the 1996 Act, namely that “the object of arbitration is to obtain the fair resolution of disputes by an impartial tribunal without unnecessary delay or expense”, and that the relevant provisions are to be construed accordingly.

The Court was guided by the well-known authorities on extensions of time, including Terna Bahrain Holding Co WLL v Al Shamsi [2012] EWHC 3282 (Comm) and the factors identified in Kalmneft JSC v Glencore International AG [2002] 1 Lloyd’s Rep 128 ). These are the (1) length and (2) explanation for the delay (did the applicant act reasonably in all the circumstances?), (3) responsibility for the delay (any contribution to the delay by the respondent or arbitrator), (4) potential prejudice to the respondent, (5)  whether the arbitration continued during the period of delay, (6) the strength of the amendment, and (7) fairness to the applicant. Factors (1) – (3) have been described by the courts as the primary factors.  

The State’s arguments

The State argued that the amendments would not delay the determination of the challenges because the date for the substantive hearing had already been fixed. It also submitted that Kalmneft factors did not generally concern amendments, and should therefore be applied with “restraint” to the more “nuanced” situation of amendments being sought to a challenge already launched in time. The State described this as a ‘bridgehead’ having been established by the commencement.

The Commercial Court’s decision

The Court accepted that the Kalmneft factors are “a guide and not a closed list”. However, the Court declined to go further than saying it could take account of the circumstance of an existing in-time claim and the fact that the amendments would not in practice delay the substantive hearing.  This is one factor to be weighed within the statutory framework; the fact the application concerns an existing challenge does not justify a different test being used. 

Applying the Kalmneft factors, the Court found that 162 days after the Award was a ‘very considerable delay, at over 5 times the section 70(3) time limit’ (factor 1). The Court was also not persuaded that the State had acted reasonably in allowing that amount of time to pass, notwithstanding the reasons given (including the involvement of new lawyers, the process of instructing a State party, and reacting to the Defence) (factor 2). Neither F nor the arbitrators had caused or contributed to the delay (factor 3). The Court acknowledged that F would not suffer irremediable prejudice by reason of the delay (factor 4), and that the arbitration had not continued during the period of delay (factor 5). The Court considered that it could not reliably conclude at the interim stage whether the amendments were strong or weak (factor 6). It would also not be unfair, in the broadest sense, to deny the State the opportunity to have the matters introduced by the amendments determined (factor 7).

Weighing these considerations together with the absence of any practical delay to the substantive hearing, the Court concluded that they did “not overcome the weight” of the substantial 162-day delay. The important objective of ‘finality’, in the sense of fixing the scope (or “compass”) of the dispute before the Court, was compromised where that scope was extended by amendment. In effect, the Court considered that it would not be appropriate to compromise finality in the process by way of a lax approach to the development of arguments to challenge the Award. To allow the challenging party to amend its case at such a late stage would not honour the statutory principle of “obtaining the fair resolution of disputes by an impartial tribunal without unnecessary delay or expense”. The opposed amendments were accordingly refused.

Importantly, the Court made clear that its decision did not limit the scope of the arguments the State could advance on the challenge as already brought. The Commercial Court is not over-technical in its approach to statements of case and, to the extent matters covered by the proposed amendments were already raised by the unamended statement of case, they remained open to the State. This was potentially significant because counsel for the State had characterised many of the proposed amendments as “refinements”’ or ‘merely developments of points already pleaded”, and similar language.

Comment and Practical Implications

The decision highlights the importance the English courts continue to place on the finality of arbitral awards. A challenging party cannot assume that filing its challenge within the 28-day deadline gives it free rein to amend that challenge after the deadline has expired.  Where a party seeks to do so, the Court will examine the application through the lens of the Kalmneft factors and the objective to resolve disputes fairly without unnecessary delay or expense, and the length of the delay may well be decisive, as it was here.

Several practical points emerge for parties and their advisers:

• Parties considering a challenge to an arbitral award should seek to identify all potential grounds of challenge within the statutory period wherever possible, avoiding the need to apply to amend the challenge later.  
• Where an amendment is necessary, it should be pursued promptly. The Court regarded a delay of 162 days as “very considerable”, and the length of the delay ultimately proved decisive notwithstanding the absence of prejudice to the opposing party. 
• A party seeking to challenge an arbitral award bears a significant procedural burden to set out its position as efficiently as possible. Arbitral awards are intended to be final; the fact there is a system for challenging them does not dilute that finality, and it is therefore imperative that challengers act with the utmost diligence in presenting their challenge in full.
• The absence of prejudice, or the fact that an amendment would not affect the hearing timetable, may not be sufficient to justify a late amendment. The Court treated those matters as relevant considerations, but held that they did not outweigh the significance of the delay. 
• Finality remains an important objective in its own right. The Court considered that finality is not only concerned with whether a challenge has been commenced in time, but also with defining the scope of the disputes that remain to be determined. Allowing a party to broaden that scope long after the statutory period has expired may be inconsistent with that objective. 
• The decision offers a measure of reassurance for a party who is refused permission to amend: it may still be able to advance points that are properly encompassed within its existing pleaded case. 

For further information, please email the authors or your usual CMS contact.

This article was co-authored by Shabbir Bokhari, Trainee Solicitor at CMS.