Amazon has suffered a significant legal setback in the United Kingdom, after the Court of Appeal on February 26, 2026, refused the company permission to challenge the certification of two major antitrust collective actions. The decision clears the path for two opt out lawsuits, one on behalf of independent third party sellers and another representing tens of millions of UK consumers, to proceed to trial with combined claims estimated at potentially over £4 billion.
Two Separate Cases, One Common Allegation
At the heart of both lawsuits is Amazon‘s “Buy Box,” the prominent purchase button that appears on product listings and accounts for approximately 80% of all purchases made on the platform. The first case, led by Andreas Stephan, Professor of Competition Law at the University of East Anglia, seeks £2.7 billion on behalf of UK third party sellers who used professional selling accounts on Amazon‘s UK marketplace between June 2018 and June 2024. The complaint alleges that Amazon abused its dominant position by unfairly favoring its own retail products and its own logistics arm, Fulfilment by Amazon (FBA), in the Buy Box algorithm, pushing up costs and fees for independent sellers.
The second case, filed by consumer advocate Robert Hammond and supported by law firm Hagens Berman EMEA, seeks over £2 billion on behalf of an estimated 51.8 million eligible UK shoppers who allegedly paid inflated prices as a direct result of the same anticompetitive conduct. Both cases were certified by the Competition Appeal Tribunal (CAT) on July 24, 2025, and proceed on an opt out basis, meaning eligible claimants are automatically included unless they actively choose to withdraw.
Amazon’s Appeal Blocked
Following the CAT‘s certification, Amazon sought to challenge the ruling at the Court of Appeal, arguing that the economic analysis underpinning the lawsuits was fundamentally flawed. The Court of Appeal denied that request on February 26, 2026, removing a key procedural obstacle and allowing both cases to move forward toward trial. The CAT had previously described Amazon‘s earlier attempt to appeal certification as “opportunistic”, refusing all grounds put forward by the company. Amazon has consistently maintained that the allegations lack merit.
A Growing Pattern of Legal Scrutiny
The UK antitrust lawsuits are part of a wider wave of regulatory and legal pressure on Amazon across multiple jurisdictions. In December 2025, a separate £900 million collective action was filed at the CAT against both Amazon and Apple, alleging the two companies struck a secret deal in October 2018 to restrict third party retailers from selling Apple products on Amazon‘s marketplace, enabling Amazon to sell Apple goods at inflated prices. The EU Commission also previously found that Amazon‘s Buy Box algorithm was anticompetitive, requiring the company to display a second competing offer when significant price differences exist.
Lessons for Brands to Avoid
For any brand operating within a marketplace ecosystem or building one of its own, this case is a significant signal. Key takeaways include:
- Algorithmic transparency matters: If a platform uses proprietary algorithms to rank or feature products, the criteria should be fair, consistent, and clearly disclosed. Favoring in house offerings without disclosure creates both regulatory and reputational risk
- Tying access to dominant services creates antitrust exposure: Conditioning premium visibility or access to programs like Prime on the use of proprietary logistics services can constitute an abuse of dominance in markets where the platform holds a significant share
- Marketplace rules must apply equally: Retailers who build marketplace platforms must treat first party and third party sellers by the same standards. Inconsistent application of rules is a core trigger for competition law complaints
- Legal costs compound over time: What begins as a platform policy decision can accumulate into billions in potential liability over the years. Building compliance checkpoints into platform design is significantly cheaper than defending them in court
- Regulators and litigants are increasingly coordinated: Competition authorities in the EU, UK, and the U.S. are sharing findings and signals. A regulatory finding in one jurisdiction can and does fuel private litigation in others
