The team pushing a £2 billion legal claim accusing Microsoft of overcharging businesses that use its software on rival clouds has called for further participants ahead of its first hearing in December.

The case in the UK's Competition Appeal Tribunal (CAT) centers on the cost – sometimes as much as four times as high – of running Windows Server on Google, AWS, or Alibaba clouds.

Microsoft: So what if it costs 4X as much to run Windows Server in AWS, Alibaba, and Google? [1]READ MORE

Filed in December 2024, the case is being spearheaded by digital markets regulation expert Dr Maria Luisa Stasi. It was given added impetus by the Competition and Markets Authority's (CMA) final findings in July that [2]Microsoft's licensing policies disadvantaged customers using its three main rivals.

Among other findings, the CMA's 637-page report [3]said : "We found significant differences relating to price and/or quality when customers use these software products on Microsoft's cloud rather than AWS or Google's."

The report also found that "Microsoft does not make certain products available to AWS and Google through their licensing agreements, and customers with existing licenses cannot bring these to AWS and Google in most instances." This affected AWS's and Google's competitive offerings.

[4]

Stasi said today: "If your organization has used Windows Server on Google, Amazon or Alibaba's cloud platforms at any point since December 2018, you have likely paid too much money. This legal action seeks to put that to an end."

[5]

[6]

She added: "Billions have been drained from budgets as a result of Microsoft's licensing practices. Cloud costs are soaring for UK businesses. Getting in touch does not commit you to anything but could result in your business or organization clawing back budget for IT costs."

The CAT hearing in December will decide whether the case can go to trial.

[7]

Microsoft had a deadline of July to file its initial response to Stasi's case. Given that Stasi is moving ahead with the action, it appears the software giant is not planning to compromise. At least not at this stage.

Then again, its legal department has had rather a lot to consider of late. [8]Google last month griped about a lack of progress on the [9]formal complaint it made last year to the EU about Microsoft's licensing on non-Azure platforms – signaling it's not going to let the matter drop.

In fact, it claimed in a blog: "It's getting worse."

[10]AWS claims 50% of Azure workloads would jump ship if licensing costs allowed

[11]Google, AWS say it's too hard for customers to use Linux to swerve Azure

[12]Microsoft still prohibits Google or Alibaba from running O365 Windows Apps

[13]EU cloud gang wins Microsoft concessions, but fair software licensing group brands them 'stalling tactic'

Last month saw the start of another CAT hearing on the [14]sale of second-hand licenses . And [15]another CAT case is in the works covering alleged overcharging on "licences for certain specified Microsoft software products (including Microsoft Office and Windows)... as a result of Microsoft's anti-competitive practices."

It's not just businesses that are kicking up a fuss. Earlier this week, Austria's Data Protection Authority ruled the company had " [16]illegally " tracked students via its 365 Education platform and used their data.

Google veep calls out Microsoft's cloud software licensing 'tax' [17]READ MORE

Microsoft is also facing multiple fights over the end of support for Windows 10. It arguably yielded an inch or two of ground – in the European Economic Area at least – by offering [18]almost no-strings-attached extended support to consumers .

Back in the UK, the CMA's findings all added up to the conclusion that "Microsoft's licensing practices are adversely impacting the competitiveness of AWS and Google in the supply of cloud services, particularly in competing for customers that purchase cloud services which use the relevant Microsoft software as an input."

[19]

The report recommended the CMA Board use its digital market powers to remedy the situation. There's been no official word on that, but it's early days yet.

The Register has asked Microsoft to comment. ®

Get our [20]Tech Resources



[1] https://www.theregister.com/2025/03/04/microsoft_blasts_uk_market_regulator/

[2] https://www.theregister.com/2025/07/31/cma_aws_microsoft_sms/

[3] https://assets.publishing.service.gov.uk/media/688b8891fdde2b8f73469544/final_decision_report.pdf

[4] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/front&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2aO_FFvI6YXjCHBB7pfSAVQAAAEg&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0

[5] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/front&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aO_FFvI6YXjCHBB7pfSAVQAAAEg&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0

[6] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/front&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33aO_FFvI6YXjCHBB7pfSAVQAAAEg&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0

[7] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/front&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aO_FFvI6YXjCHBB7pfSAVQAAAEg&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0

[8] https://www.theregister.com/2025/09/25/google_microsoft_cloud_complaint/

[9] https://www.theregister.com/2024/09/25/google_ms_ec_complaint/

[10] https://www.theregister.com/2025/04/16/aws_microsoft_license_harms/

[11] https://www.theregister.com/2025/04/17/swapping_linux_for_microsoft_is_hard/

[12] https://www.theregister.com/2023/08/25/microsoft_google_alibaba_windows_apps/

[13] https://www.theregister.com/2025/07/18/cispe_microsoft_concessions/

[14] https://www.theregister.com/2025/09/08/microsoft_valuelicensing_latest/

[15] https://microsoftclaim.com/faq/

[16] https://www.theregister.com/2025/10/13/microsoft_365_education_gdpr/

[17] https://www.theregister.com/2023/06/01/google_microsoft_cloud_complaints/

[18] https://www.theregister.com/2025/09/26/not_in_eu_and_want/

[19] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/front&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33aO_FFvI6YXjCHBB7pfSAVQAAAEg&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0

[20] https://whitepapers.theregister.com/