Competition claims and the CAT regime
The Competition Appeal Tribunal's collective proceedings regime has reshaped how competition law damages reach consumers and businesses, and the Mastercard class action illustrates both its promise and its structural tensions.
Competition claims and the CAT regime
The Competition Appeal Tribunal's collective proceedings regime represents the most significant structural shift in English competition litigation in a generation. Before the Consumer Rights Act 2015 introduced opt-out collective proceedings to the CAT, competition damages in England and Wales were largely the preserve of well-resourced corporate claimants capable of sustaining years of expensive litigation. Individual consumers and small businesses harmed by cartel conduct or abuse of dominance had no realistic mechanism for recovery. The regime that emerged from the 2015 reforms changed that calculus fundamentally, and the Mastercard class action, formally Walter Hugh Merricks CBE v Mastercard Incorporated and Others, became the vehicle through which the courts and the Tribunal worked out what the new framework actually meant in practice. Understanding how that process unfolded, and what it reveals about the operating logic of the CAT regime, is essential for any practitioner, funder, or operator working in this space.
What the market usually gets wrong
The dominant misconception about the CAT's collective proceedings regime is that it is simply a transplant of the American class action model onto English soil. That framing is understandable. The opt-out mechanism, the representative plaintiff structure, and the role of third-party litigation funding all have superficial American analogues, but that comparison obscures the ways in which the English regime is structurally distinct and, in several respects, more demanding.
The certification stage in the CAT, known as the collective proceedings order or CPO application, is not a low threshold. The Tribunal must be satisfied that the claims are suitable for collective proceedings, that the proposed class representative is adequate, and that there is a workable methodology for assessing aggregate damages across the class. The Supreme Court's 2020 judgment in Merricks made clear that the certification stage should not become a mini-trial on the merits, but it equally confirmed that the methodology question is a genuine and substantive one. A proposed class representative cannot simply assert that damages can be assessed in aggregate and expect certification to follow automatically.
This matters because it shapes the economics of the regime from the outset. The investment required to produce a credible expert methodology at the CPO stage is substantial. Funders and law firms entering this market on the assumption that certification is a formality have consistently underestimated the front-loaded cost and risk. The Mastercard class action itself spent years in procedural and appellate litigation before the substantive merits were ever examined, and that trajectory is not exceptional. It is the predictable consequence of a regime that takes the certification question seriously.
A secondary misconception is that opt-out proceedings automatically produce large, manageable classes with clean membership boundaries. In practice, defining the class with sufficient precision to satisfy the CAT while remaining broad enough to justify the economics of collective proceedings is a genuine drafting and expert challenge. The interaction between class definition, limitation periods, and the treatment of indirect purchasers creates complexity that practitioners accustomed to individual commercial litigation frequently underestimate.
What actually changes when you look at the operating layer
Strip away the procedural surface and the CAT collective proceedings regime is, at its core, a mechanism for aggregating dispersed, individually uneconomic claims into a litigation vehicle that can sustain the cost of expert evidence, disclosure, and trial. The operating logic is therefore fundamentally about economics rather than law. Whether a collective action is viable depends less on the strength of the underlying competition law case than on whether the aggregate damages are large enough, the class is sufficiently defined, and the methodology for quantifying loss is credible enough to attract and retain funding.
This has several practical consequences that are not always visible from the outside. First, the relationship between the class representative and the litigation funder is structurally different from a conventional funded case. The class representative owes duties to the class as a whole, not to the funder, and the CAT has explicit powers to scrutinise funding arrangements and ensure they do not compromise those duties. The Tribunal's approach to funding arrangements at the CPO stage and beyond means that funders cannot simply import the contractual structures they use in bilateral commercial litigation without adaptation.
Second, the aggregate damages methodology is not merely an expert exercise. It is the central commercial and legal document in the case. The methodology must be capable of producing a damages figure that is both legally defensible and practically distributable. In a large opt-out class, the mechanics of distribution, including how unclaimed funds are handled, what happens to class members who cannot be identified, and how the representative's costs interact with the damages pool, are operational questions that must be resolved before certification, not after judgment.
Third, the CAT's case management approach differs materially from the Commercial Court. The Tribunal is specialist, moves at its own pace, and has developed a body of procedural practice that is still evolving. Practitioners who treat CAT proceedings as a variant of High Court commercial litigation tend to find that the Tribunal's expectations around expert evidence, disclosure, and case management conferences do not map cleanly onto their existing workflows.
For anyone seeking a broader orientation to how collective redress mechanisms operate across different contexts, the class actions and collective redress pillar sets out the structural framework within which the CAT regime sits.
Commercial consequences
The commercial consequences of the CAT regime's maturation are being felt across several distinct markets simultaneously. For law firms, the regime has created a new category of high-value, long-duration mandates that require a different capital and resourcing model from conventional litigation. The front-loaded investment in expert evidence, the extended certification process, and the possibility of multiple rounds of appellate review mean that even well-resourced firms face genuine balance sheet questions about how many collective proceedings they can carry at any one time.
For litigation funders, the CAT regime has become one of the most scrutinised areas of the market. The Supreme Court's judgment in PACCAR in 2023, which held that litigation funding agreements meeting the definition of damages-based agreements are unenforceable without compliance with the relevant regulatory framework, created immediate uncertainty about the enforceability of funding arrangements across the CAT's collective proceedings docket. The legislative response to PACCAR, together with the ongoing debate about whether and how to regulate litigation funding more broadly, has added a further layer of commercial uncertainty to an already complex operating environment. Funders with significant exposure to CAT collective proceedings have had to revisit their portfolio assumptions in ways that were not anticipated when those positions were built.
For defendant businesses, particularly those in financial services, payments, and other sectors where the CAT's jurisdiction is most active, the regime has changed the risk calculus around competition compliance. The prospect of opt-out collective proceedings covering potentially millions of affected individuals means that the tail risk from competition infringement is now materially larger than it was under the pre-2015 framework. That shift has not been uniform in its effect. Some sectors have invested heavily in competition compliance infrastructure in response, while others have been slower to adjust, but the directional pressure is clear.
The Mastercard class action is the most visible example of these dynamics, but it is not the only one. A growing pipeline of CAT collective proceedings across sectors including financial services, retail, and digital markets means that the commercial consequences described above are not confined to a single high-profile case. They reflect the structural operation of a regime that is now producing a body of precedent and practice with real market-wide implications. Further analysis of how these dynamics play out in related litigation contexts is available in the writing section of this site.
Where the market is likely to move next
Several forward-looking developments are worth tracking for anyone operating in or adjacent to the CAT collective proceedings market.
The regulatory treatment of litigation funding is the most immediate variable. The PACCAR judgment and the subsequent legislative debate have created a period of genuine uncertainty, and the resolution of that uncertainty, whether through primary legislation, regulatory guidance, or further judicial development, will materially affect the economics of funded collective proceedings. Funders, law firms, and class representatives all have significant interests in how this question is resolved, and the outcome will shape the structure of funding arrangements for years to come.
The CAT's developing approach to certification methodology is a second area of evolution. As the Tribunal accumulates experience with CPO applications across different sectors and fact patterns, its expectations around expert evidence and aggregate damages methodology are becoming more defined. That process of definition cuts both ways: it creates greater predictability for well-prepared applicants, but it also raises the bar for those who approach certification without adequate expert support.
The interaction between CAT collective proceedings and follow-on actions in the High Court is a third area of ongoing development. The relationship between infringement decisions by the Competition and Markets Authority or the European Commission and subsequent damages claims in the CAT involves questions of binding effect, limitation, and jurisdiction that are still being worked through in the case law. As the CMA's enforcement activity increases, particularly in digital markets, the pipeline of potential follow-on collective proceedings is likely to grow, and the procedural questions around how those claims are managed will become more pressing.
For practitioners and operators seeking to understand how these developments connect to the broader landscape of third-party funding and litigation economics, the about page sets out the analytical framework that informs the approach taken across this site.
What this means in practice
The CAT collective proceedings regime is not a simple or forgiving mechanism. It rewards preparation, expert investment, and a clear-eyed understanding of the economics at every stage from class definition through to distribution. The Mastercard class action has demonstrated that even well-resourced, carefully constructed collective proceedings can spend years in procedural and appellate litigation before reaching the merits, and that the certification stage is a genuine substantive hurdle rather than an administrative formality.
For law firms, the practical implication is that collective proceedings require a distinct resourcing and capital model that cannot simply be grafted onto existing litigation infrastructure. For funders, the PACCAR judgment and the ongoing regulatory debate mean that the enforceability and structure of funding arrangements must be kept under active review rather than treated as settled. For defendant businesses, the regime means that competition compliance is no longer merely a regulatory question. It is a balance sheet question, because the aggregate exposure from opt-out collective proceedings covering large consumer classes is now a material financial risk.
The broader lesson from the CAT regime's first decade of operation under the 2015 framework is that collective redress mechanisms of this kind do not simply transplant legal rights into recoverable damages. They create a new operating environment with its own economics, its own procedural logic, and its own set of commercial risks and opportunities. Navigating that environment effectively requires an understanding of the regime at the level of its actual operating mechanics, not merely its surface legal structure.
For those wishing to discuss how these dynamics apply to a specific matter or portfolio, the contact page provides the relevant details.
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This essay sits within the broader class actions and collective redress at uk scale theme, with nearby routes into the archive, related background pages, and Craig's wider point of view.
Fact ledger
Reviewed 24 April 2026 · Primary keyword: mastercard class action
The Consumer Rights Act 2015 introduced opt-out collective proceedings to the Competition Appeal Tribunal, creating a mechanism for aggregating individually uneconomic competition damages claims on behalf of consumers and small businesses.
The 2015 reform fundamentally altered the economics of competition litigation in England and Wales, making the CAT regime the primary vehicle for large-scale consumer redress in competition cases and creating a new market for specialist law firms and litigation funders.
The UK Supreme Court's 2023 judgment in PACCAR held that litigation funding agreements meeting the statutory definition of damages-based agreements are unenforceable without compliance with the relevant regulatory framework, creating immediate uncertainty across the CAT's collective proceedings docket.
PACCAR forced funders and class representatives to revisit the enforceability of existing funding arrangements and accelerated the legislative and regulatory debate about how litigation funding should be governed, with direct consequences for the commercial viability of funded collective proceedings in the CAT.
The Supreme Court's 2020 judgment in Merricks v Mastercard confirmed that the CAT's certification stage should not become a mini-trial on the merits, but equally affirmed that the methodology for assessing aggregate damages is a genuine and substantive requirement that must be addressed at the collective proceedings order stage.
The Merricks judgment set the standard for CPO applications across the CAT regime, establishing that a credible aggregate damages methodology is a threshold requirement for certification and that the front-loaded expert investment required to meet that standard is a structural feature of the collective proceedings market rather than an anomaly.