Background

On 26 February, 2026, the UK Court of Appeal cleared the way for sellers and consumers to sue Amazon UK by ruling against the retailer’s attempt to appeal two Competition Appeal Tribunal (CAT) cases.

In 2025, the CAT had certified both class action cases on an opt-out basis.

Amazon attempted to block the two lawsuits by arguing that the cases should not be certified to proceed. The Court of Appeal refused permission to appeal the CAT rulings.

The two cases are now proceeding to trial, with a total claim value of £4 billion.

Case 1: Robert Hammond v Amazon.com, Inc & Others

Consumer advocate Robert Hammond is bringing a case valued at up to £1.3 billion on behalf of approximately 49.4 million Amazon UK customers for abuses of dominance that resulted in those customers being overcharged.

Hammond’s case centres around Amazon’s ‘Buy Box’ feature, which he alleges is used to maximise the company’s own profits. Specifically, he claims that the algorithm results in an abuse of dominance by favouring Amazon’s product offers and those of sellers that use ‘Fulfilment by Amazon’ (FBA), and suppresses any lower-cost offers from sellers using ‘Fulfilment by ’.

The CAT certified Hammond’s case on July 24 2025, enabling him to proceed with his claim as class representative for consumers who purchased items from Amazon.co.uk between 1 October 2015 and 7 June 2023.

Amazon UK applied to the Court of Appeal for permission to appeal the CAT’s certification decision based on an error in law in the CAT’s assessment of the litigation funding agreement between Hammond and his funder.

When determining whether it is ‘just and reasonable’ to appoint a person as representative, the CAT must consider whether he or she would ‘fairly and adequately act’ in the interests of class members – which in turn requires the tribunal to take into account whether the representative has a plan for the proceedings that satisfactorily includes estimates of cost, fee, and disbursement arrangements.

Amazon argued that, when it came to Hammond’s funding, the potential return to the funder was ‘wholly unreasonable’ and higher than what the CAT had called ‘not defensible’ in an earlier case – the CAT erred in law by applying a default rule that it interpreted from the Court of Appeal decision in Gutmann, that scrutinising the reasonableness of funding arrangements should be left until the end of the proceedings.

The Court of Appeal rejected Amazon’s argument – stating that the CAT’s reference to what had been endorsed in Gutmann was to the point that the CAT can review a funder’s return at any stage of the proceedings. The court noted Gutmann simply stated that the amount of funder’s return is subject to the scrutiny and approval of the CAT – the final decision (that the reasonableness of the funder’s return would be addressed at the time of distribution) was an outcome based solely on the facts of that particular case.

 As the tribunal stated in its certification judgment, referring to the claimant allegations that “consumers who bought from sellers supplying FBA would have paid less for the same purchase by either buying from a lower-priced alternative supplier or from the same supplier at a lower .”

Case 2: Professor Andreas Stephan v Amazon.com Inc & Others

A second case against Amazon UK, worth up to £2.7 billion, has been brought by Professor Andreas Stephan on behalf of over 200,000 UK-domiciled third-party retailers who sold items on the platform between June 2018 and June 2024.

Stephan alleges that Amazon abused its dominant marketplace position though a number of unlawful practices. These include using seller data to gain unfair advantage by launching competing Amazon-branded products, and ‘self-preferencing’ when selecting products for the ‘Buy Box’ feature by favouring its own listings and those sold using Amazon’s logistics and delivery services.

According to Stephan, these practices result in sellers making fewer sales, paying higher prices for logistics, and paying higher referral and fulfilment fees.

The CAT certified Stephan’s case on July 24 2025.

Amazon UK applied to the Court of Appeal for permission to appeal against the certification decision.

Amazon claimed that the CAT erred in finding no actual or potential conflict of interest within the class of third-party sellers. Its argument was based on two alleged abuses – favouring Fulfilment by Amazon (FBA) sellers over Fulfillment by Merchant (FBM) in ‘Featured Offer’, and making the ‘Prime’ label contingent on FBA.

The aggregate damages claim is based on indirect effects rather than direct loss/gain from diverted sales (since a loss to an FBM seller from a diverted sale is usually offset by a gain to a FBA seller). However, this offset doesn’t if sales are diverted to overseas FBA sellers, or differing profit margins, so a ‘diversion rate’ needs to be factored in.

Amazon argued that this incentivizes the representative to argue for a higher diversion rate to maximise aggregate damages at the liability stage. However, FBA sellers would want a lower diversion rate at distribution. This, according to Amazon, creates a conflict.

The Court Rejected Amazon’s argument since expert evidence indicated that an FBA seller’s loss from the fee overcharge would always exceed the profit from diverted sales, so FBA sellers would always want a higher diversion rate too. The Court held the CAT was entitled to conclude there was no possibility of conflict at this stage.

Amazon faces increasing scrutiny in the UK and beyond

Both the Hammond and Stephan class-action lawsuits are expected to go to trial in front of the CAT in 2027.

The Court of Appeal ruling is one of the latest decisions in growing legal and regulatory scrutiny around how Amazon’s treats sellers and consumers. In 2022, the European Commission found that Amazon had engaged in self-preferencing in markets such as France, Germany, and Spain. In 2023, the UK Competition and Markets Authority found that Amazon’s marketplace practices disadvantaged independent sellers, and secured commitments from it to reform Buy Box.

We will continue to report on the progress of these proceedings.