UK’s Competition Appeal Tribunal greenlights multi-billion pound collective action against Amazon over anticompetitive conduct targeting third-party sellers.

The UK Competition Appeal Tribunal (“CAT”) has approved a multibillion-pound collective action against Amazon to proceed to trial.

A judgment handed down on  24 July 2025 by the CAT confirmed that an “opt out” collective proceedings claim against Amazon can move ahead, paving the way for over 200,000 third-party sellers to claim compensation. 

The claim, which currently stands in excess of £2.7bn against Amazon, sees the online retail platform accused of engaging in anticompetitive conduct.

The claim, brought by Andreas Stephan, Professor of Competition Law at the University of East Anglia, focuses on multiple anti-competitive practices by Amazon that have harmed UK third-party sellers with “professional” selling accounts on Amazon. Any UK domiciled third-party seller that used a professional selling account to sell products on the UK version of the Amazon marketplace between June 2018 and June 2024 will be automatically part of the claim, unless they choose to opt out. 

Professor Stephan claims that Amazon has abused its dominant position in the market for the supply of e-commerce marketplace services to third-party sellers to reach customers in the UK by engaging in abusive behaviour that:

• unfairly advantages its own retail products, harming third-party sellers;
• unfairly advantages Amazon Retail offers when selecting which offers are displayed in the “Buy Box”;
• unfairly advantages its own logistics/fulfilment arm (“Fulfilment by Amazon” or “FBA”), harming other logistics/fulfilment providers, and in turn, third-party sellers;
• unfairly conditions access to Amazon Prime on the use of FBA; and
• distorts inter-platform competition by making it harder for third-party sellers to sell cheaper on other platforms. 

As a result of these abuses, says Professor Stephan, third-party sellers have lost sales, faced increased costs and paid higher fees to Amazon for its services than they would have under normal conditions of competition. 

The CAT has now made a collective proceedings order, confirming its decision to certify the claim, authorising Professor Stephan to act as the class representative and permitting the claim to proceed to trial.

Professor Stephan commented: “Recognition of our case by the Tribunal is an important first step in compensating the thousands of UK Amazon sellers who have lost revenues because of the tech giant’s unfair practices.”

Professor Stephan’s claim is backed by a legal team composed of competition litigation and digital markets specialists Geradin Partners, Kieron Beal KC (Blackstone Chambers), Daniel Carall-Green, Hannah Bernstein, and Christopher Monaghan (Fountain Court Chambers). Professor Stephan is also supported by a strong team of economists led by Dr George Houpis of Frontier Economics whose preliminary expert report was praised by the Tribunal as “comprehensive and very detailed”.

Founding Partner of Geradin Partners, Damien Geradin, said: ““Amazon, one of the world’s largest companies, has engaged in manifest abuses of its dominant position as recognized by competition authorities in the EU and the UK. Amazon is also subject to a lawsuit filed by the US Federal Trade Commission for anticompetitive conduct. This class action gives sellers the opportunity to seek redress for the significant harm they have suffered”. 

Professor Stephan is also assisted by a vastly experienced consultative council, which includes former Supreme Court president Lord Neuberger, Stephen Robertson, former Director General of the British Retail Consortium, and Sue Prevezer KC, a senior barrister with over 30 years' experience in commercial litigation. 

Professor Stephan’s claim is funded by Innsworth Capital.

Further information can be found at: www.amazon3psellerclaim.com. This includes an online form to enable third-party sellers to register for updates on the claim, as well as to get in touch with Professor Stephan.