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On 18 December 2025, the UK Supreme Court handed down its judgment in Evans v Barclays Bank Plc and others [2025] UKSC 48, delivering a landmark ruling on the certification of opt-out collective proceedings. The decision was reached in Mr Evans’ application to bring opt-out proceedings following-on from the European Commission’s May 2019 decisions regarding several banks’ conduct in the foreign exchange spot markets.
Whereas the Court of Appeal had said that the merits of a claim were a “neutral factor” in the choice between certification on an opt-out or opt-in basis, the Supreme Court reversed that ruling and held that the weakness of the claim militated against certification on an opt-out basis. The Supreme Court also held, amongst other things, that the practicability of a claim being pursued on an opt-in basis if opt-out certification were refused was not a relevant factor.
In this blog post we discuss the reasoning behind the Supreme Court’s decision, along with the important takeaways for parties to UK collective proceedings.
At first instance, the Competition Appeal Tribunal had held that the case should not proceed on an opt-out basis due to its weak merits concerning the causal link between the alleged infringement and the claimants' losses. The Court of Appeal reversed that decision, reasoning that the relative strength and/or weakness of the case should not be factored into the decision of whether to proceed on an opt-in or opt-out basis. The Supreme Court was then required to determine the role of merits in assessing opt-in or opt-out proceedings at the certification stage.
The Supreme Court upheld the Tribunal’s original position that, whilst the merits were not relevant to the question of certification itself, the Tribunal’s Rules explicitly permitted it to consider the strength of claims when determining whether proceedings should be opt-in or opt-out.
The Supreme Court identified three reasons why allowing a weak claim to proceed on an opt-out basis would be unjust:
(i) The parties would not be on equal footing given the leverage which opt-out proceedings would afford to the claimants.
(ii) The expense caused to the defendant would be disproportionate to the case.
(iii) It would not be an appropriate use of the Tribunal’s time and resources.
The ‘leveraging effect’ of class actions was central to the Court’s reasoning. The judges considered that permitting a weak claim to proceed on an opt-out basis placed defendants under commercial pressure to settle even where the case was likely to fail at trial. The Supreme Court rejected the Court of Appeal’s view that the claim should proceed because disclosure would generate material which would overcome concerns about the claim’s strength, holding that the speculation that “something may turn up” was not a sufficient reason to compel defendants to incur the major inconvenience and expense of a disclosure exercise.
At its core, the Supreme Court’s decision reflected the two-sided nature of the ‘access to justice’ principle – balancing the vindication of claimants’ rights against the protection of businesses from the burden of defending unmeritorious claims. For this reason, the Court was clear that the fact that a claim would collapse if not pursued on an opt-out basis does not constitute a ‘trump card’.
The practicability of opt-in proceedings is the other factor which the Tribunal’s Rules expressly identify as relevant to the choice between opt-in and opt-out. In its ruling, the Supreme Court identified this as the other-side-of-the-coin to the leveraging effect of opt-out proceedings; if opt-in proceedings are practicable then the risks associated with that leveraging can be avoided. A paradigm case where opt-in proceedings would often not be practical is a claim which has a large number of class members with very small claims. In the present case, the claims of sophisticated class members with large claims predominated but there was a small rump of class members with smaller claims. The Court held that the practicability of opt-in proceedings must be considered separately for each group, but it was difficult to see why the large institutions should bolster their position because of the presence of a small set of low-value claims.
The Supreme Court emphasised that the CAT’s expertise in economic assessments and collective proceedings management supported its wide discretion in case-specific determinations. Although there was room for disagreement about the Tribunal’s inferences, it was not for the Court of Appeal to substitute its own assessment for the Tribunal’s and its jurisdiction was limited to confirming if there was an error of law in the Tribunal’s judgment.
The Supreme Court’s decision mandates a change in tack in collective proceedings jurisprudence. The Tribunal and the Court of Appeal now have the benefit of a clear ruling, from the highest judicial authority, that unmeritorious claims are (other things being equal) not suitable for certification as opt-out proceedings because of the burden that they place on defendants. As the Court explained, this can be the case even where a claim has survived a strike-out or summary judgment application: the bar for surviving these is very low and the unfairness of a claim to defendants does not drop away simply because a claim has some, albeit limited, merit.
The Court’s decision on the practicability of opt-in proceedings also opens up new considerations during the certification process. Claims covering classes which incorporate small class members with claims of low value and large class members with claims of significant value may now need to be cast as opt-out claims for smaller class members and opt-in claims for larger class members. Where opt-in claims on behalf of large class members now emerge, defendants and the Tribunal are more likely to benefit from the active participation of sophisticated opt-in class members – adding a new dimension to arguments regarding issues such as disclosure, causation and quantification of loss. If opt-in claims now become more common, settlement dynamics may also shift because participating class members will be in a position to represent their own financial interests in discussions with the class representative or with defendants directly.
We would like to thank Abinand Lagisetti for his assistance in the preparation of this article.
9 January 2026