TL;DR
A collective claim against Microsoft is before the UK Competition Appeal Tribunal, alleging the company overcharged organisations that run Windows Server on rival clouds. The tribunal must decide whether the case can proceed to a full trial next year; potential damages could exceed £2 billion if the claim succeeds.
What happened
Dr Maria Luisa Stasi has brought a collective claim in the UK alleging Microsoft used its market position to make running Windows Server on competing cloud platforms more expensive, steering customers toward Azure. The Proposed Class represents roughly 59,000 organisations across sectors; Stasi's legal team says the average member suffered losses in the tens of thousands of pounds. The claim was lodged in December 2024 and this week's hearing at the Competition Appeal Tribunal (CAT) will determine whether a Collective Proceedings Order is granted so the matter can proceed to trial, planned for next year if allowed. The claimant estimates trial costs at £18.4 million and has a litigation funding agreement with Litigation Capital Management to cover adverse costs. Microsoft has dismissed the claim as opportunistic and linked it to complaints previously raised by Google. The UK Competition and Markets Authority earlier found Microsoft charged higher prices for software used on rival clouds, and the company has faced related scrutiny in Europe.
Why it matters
- If permitted to proceed and successful, the claim could expose Microsoft to more than £2 billion in compensation.
- A ruling against Microsoft could establish legal precedent on access, interoperability and fair pricing in the cloud market.
- The case highlights ongoing regulatory and commercial scrutiny of cloud licensing practices and their competitive effects.
- A collective judgment could affect thousands of businesses that rely on Windows Server across multiple cloud providers.
Key facts
- Proposed Class Representative: Dr Maria Luisa Stasi.
- Proposed Class size: approximately 59,000 organisations across industries.
- Allegation: Microsoft overcharged customers running Windows Server on rival clouds (e.g., Google, AWS) to favour Azure.
- Claim filed in December 2024; CAT hearing in December 2025 is to decide whether it can proceed.
- Potential compensation exposure stated as more than £2 billion if the abuse claim succeeds.
- Estimated costs to take the case to trial: £18.4 million, according to the PCR.
- There is a litigation funding agreement with Litigation Capital Management to indemnify the PCR against adverse costs.
- Microsoft called the action opportunistic and tied it to earlier complaints lodged by Google.
- The UK Competition and Markets Authority found in July 2025 that Microsoft charged higher prices for software used on rival cloud services.
What to watch next
- Whether the Competition Appeal Tribunal grants a Collective Proceedings Order allowing the case to proceed to a full trial (this is the current decision at issue).
- If the CAT allows the claim to proceed, look for scheduling of the trial expected next year and any narrowing of issues to be tried.
- Whether any additional businesses or funders join the Proposed Class or support the litigation (not confirmed in the source).
Quick glossary
- Collective Proceedings Order (CPO): A court order in the UK that permits a group of claimants with similar legal claims to bring a collective action on behalf of a larger class.
- Competition Appeal Tribunal (CAT): A specialist UK tribunal that hears and decides competition and economic regulatory cases, including collective actions.
- Litigation funding agreement: A contract in which a third party provides financial support for legal proceedings, often covering costs or adverse costs in return for a share of any settlement or award.
- Market power: The ability of a firm to raise prices or restrict competition in a market, typically because of its size, share or control over essential products or services.
Reader FAQ
Who brought the claim against Microsoft?
The Proposed Class Representative is Dr Maria Luisa Stasi.
What is Microsoft accused of?
The claim alleges Microsoft overcharged organisations that run Windows Server on competing cloud platforms to steer customers to Azure.
What could happen if the claim succeeds?
The source says Microsoft could face more than £2 billion in compensation if found to have abused its market power.
Has Microsoft responded to the allegations?
Microsoft has described the case as opportunistic and said it ties into complaints previously raised by Google.
Will the case go to trial?
The CAT must first grant a Collective Proceedings Order; if it does, the claim is expected to move to a full trial next year.
SAAS 19 Here we go again: Microsoft in UK court over cloud licensing Competition Appeal Tribunal to decide if multibillion-pound overcharging case can go to trial Richard Speed Fri 12 Dec 2025 //…
Sources
- Here we go again: Microsoft in UK court over cloud licensing
- Microsoft fights $2.8 billion UK lawsuit over cloud …
- Microsoft back in court over unfair cloud licensing claims
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