Microsoft is facing a collective action lawsuit in the United Kingdom seeking up to £2.1 billion ($2.8 billion) in damages for alleged anti-competitive practices related to its Windows Server software. The claim, filed on April 23, 2026, at the Competition Appeal Tribunal in London, asserts that the technology company leveraged its dominance in the server operating system market to penalize businesses that opted for competing cloud infrastructure providers.
The lawsuit is led by Maria Luisa Stasi, a competition law specialist, who is acting as the proposed class representative for thousands of UK-based organizations. The filing alleges that Microsoft’s licensing policies, specifically those introduced or modified between 2019 and 2022, created a financial barrier for companies wishing to run Windows Server on platforms such as Amazon Web Services, Google Cloud, or Alibaba Cloud. According to the claimants, these policies forced customers to pay significantly higher prices—often referred to as a cloud tax—to use Microsoft software on rival clouds compared to the costs associated with Microsoft’s own Azure platform.
The legal team representing the claimants argues that Microsoft’s conduct restricted choice and stifled competition within the UK’s cloud computing market. The claim details how Microsoft allegedly tied its dominant software products to its cloud infrastructure, making it economically unfeasible for many enterprises to migrate away from Azure or to maintain a multi-cloud strategy. The sought-after damages of £2.1 billion are intended to compensate UK businesses for the excess costs incurred due to these licensing restrictions over several years.
In official statements regarding its licensing frameworks, Microsoft has historically maintained that its policies are designed to provide flexibility and security for customers. The company has previously argued that its pricing structures reflect the value of integrated services and that it has made significant efforts to address regulatory concerns. In 2024, Microsoft reached a settlement with the Cloud Infrastructure Services Providers in Europe to resolve similar complaints; however, that settlement did not include the UK market and did not provide for retrospective financial compensation for affected businesses.
The filing of this lawsuit comes amid heightened regulatory scrutiny of the cloud sector in the United Kingdom. The Competition and Markets Authority is currently engaged in a broad investigation into the dominance of major cloud providers. This class action represents an opt-out proceeding, meaning that any UK business that purchased Windows Server licenses for use on third-party cloud platforms during the specified period is automatically included in the claim unless they explicitly choose to opt out. The Competition Appeal Tribunal will now determine whether the case can proceed to a full trial.