The Competition and Markets Authority (CMA) has opened a formal investigation into Microsoft amid concerns the tech giant may have misled millions of customers over changes to its popular Microsoft 365 subscription service.

For those who don't know, Microsoft Office contains some of the most popular productivity apps on the planet — with many relying on this software every day at work, school, and home. Office includes everyday names like Microsoft Word, Excel, PowerPoint, Outlook, and more.

These days, Microsoft offers these apps as part of a monthly subscription called Microsoft 365 (née Office 365), which means you'll always get access to the latest iteration and features, can work in a web browser, and store documents online to access from any device.

Now the CMA is scrutinising whether subscribers received sufficiently clear information when the company folded its Artificial Intelligence (AI) tool, Copilot, into existing Personal and Family plans.

The changes trace back to January 2025, when Microsoft began offering existing subscribers access to Copilot and other new AI features at no additional charge for the remainder of their current billing period.

However, once that free window expired, customers were automatically shifted onto a pricier plan unless they actively chose an alternative or cancelled altogether.

For those on annual Personal or Family subscriptions, this meant paying £25 more annually than before.

The following plans are currently available for subscribers:

Microsoft did make a Classic plan available — which is the same package subscribers had previously enjoyed, at the original price. However, this option was only open for a limited time during the re-enrolment window.

The CMA is now examining whether the company made these choices sufficiently obvious to customers before their subscriptions renewed.

Hayley Fletcher, the CMA's senior director for consumer protection, said: "People across the UK rely on Microsoft 365, whether they're studying, sending emails or managing household finances.

"At a time when household budgets are squeezed, it's important that people are clear on the price and the subscription plans available, so they can find the right deal for them."

Ms Fletcher added: "When a business changes its subscription plans, customers need clear and timely information about their options. Our investigation will consider whether Microsoft customers were misled and ended up paying more as a result."

A Microsoft spokesperson said: "Consumer trust and transparency are priorities for Microsoft, and we are reviewing the CMA's claims in detail. We remain committed to working constructively with the regulator as their inquiry progresses."

The CMA has not yet reached any conclusions on whether Microsoft breached the law.

The regulator wants to establish whether people understood what they were signing up for — and whether they ended up paying more as a consequence.

In Australia, the consumer regulator has already brought Microsoft before the courts, alleging that roughly 2.7 million subscribers were misled over Copilot-related pricing alterations and that the cheaper Classic option was effectively concealed until a customer attempted to cancel.

Italy's competition authority has also opened its own proceedings, examining similar grievances and extending its review to encompass Microsoft Designer alongside Copilot.

Taken together, the investigations across three continents point to growing regulatory unease about how major software firms are weaving AI upgrades into established subscription products.