Microsoft contests a major UK lawsuit alleging inflated licence costs for Windows Server on rival cloud platforms, as regulators examine cloud market competition.
Collective claim over Windows Server licensing
Microsoft is defending a collective lawsuit in the United Kingdom that alleges it overcharged UK businesses for running Windows Server software on non-Azure cloud platforms, a practice said to disadvantage customers that chose Amazon Web Services (AWS), Google Cloud, or Alibaba Cloud over Microsoft’s own cloud service. The claim was filed with the Competition Appeal Tribunal (CAT) and seeks about £2.1 billion ($2.81 billion) in damages.
The lawsuit represents around 60,000 UK businesses, according to the December 2025 report. Maria Luisa Stasi, a competition lawyer, leads the collective action.
A similar claim filed in 2024 sought more than £1 billion in damages and contained comparable allegations of anti-competitive pricing when Microsoft’s licences were used on AWS, Google Cloud, or Alibaba Cloud rather than Azure.
Claims of anti-competitive pricing
The claimants say Microsoft’s licensing terms make it more expensive for UK companies to run its software on rival cloud providers than on Azure, and that this incentivises use of Azure by pricing out competition.
Earlier media reporting on similar allegations noted that pricing differences could be up to four times higher on rival platforms than on Azure, although this specific figure has not been independently verified by primary filings publicly available.
Tribunal process and Microsoft’s response
The CAT is weighing whether to certify the collective action, a necessary step before full trial proceedings. Certification determines how damages might be calculated and assessed against Microsoft.
Microsoft has responded by arguing the claim lacks a viable method for calculating losses and should be dismissed at an early stage. The company also states that the cloud market remains competitive and dynamic despite the allegations.
Regulatory scrutiny
The UK’s Competition and Markets Authority (CMA) has separately examined cloud licensing practices and concluded that Microsoft’s terms could disadvantage rivals such as AWS and Google Cloud.
The CMA’s findings influenced broader industry and claimant arguments about market competition, though CMA’s final remedies or official order texts are not directly cited here.
What this means for UK businesses
If certified and successful, the collective action could entitle qualifying UK organisations to compensation for alleged overcharges. The case also reflects mounting scrutiny of major cloud providers’ licence frameworks and how they affect competition among cloud infrastructure services.
