英国納税者に警告：HMRC職員2万8千人がAIコパイロットを導入

HMRC is betting big on Microsoft Copilot, rolling it out to tens of thousands of staff after a Whitehall trial estimated it saved each user roughly 26 minutes of time per day.

The department has dished out about 28,000 Microsoft Copilot licenses and is preparing to switch on agentic-style features, with chief AI officer James Mitton pitching a future where HMRC becomes "the most AI-enabled tax authority on the planet."

"We have rolled out 28,000 Copilot licenses," Mitton said at the Think AI for Government event in London last week. The plan, he added, is to give staff "some fairly potent AI tools that they can safely play with."

This didn't come out of nowhere. Back in June 2025, the Government Digital Service ran a 20,000-civil servant trial across a dozen departments, including HMRC, to gauge whether it was genuinely useful or just good at knocking out polite emails.

The answer was: eh, sort of.

Participants in the trial reported an average time saving of 26 minutes a day, with "over 70 percent" saying it cut time spent searching for information and doing mundane tasks, while 82 percent said they wouldn't want to go back to life without it.

The report is a bit less upbeat once you get past the headline numbers. It points to "limitations… when dealing with complex, nuanced, or data-heavy aspects of work," and raises concerns about "security and the handling of sensitive data."

In other words, fine for drafting emails, less so for anything that actually matters – which makes HMRC's enthusiasm for pushing it into "Official Sensitive" workflows feel ambitious.

Mitton, for his part, is keen to stress this isn't HMRC's first brush with AI. The department claims around £8 billion in benefits from earlier automation efforts used to close the tax gap, treating Copilot as a bolt-on to current systems, not a rethink.

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Still, there's a difference between back-end number crunching and handing thousands of staff a generative system that happily hoovers up whatever documents they already have access to – especially when, as previous trials warned, that access isn't always as tidy as it should be.

It also lands in a government IT estate that hasn't exactly nailed the basics. Stale and duplicated gov.uk content has already tripped up AI systems, feeding them outdated or conflicting information, which isn't a great starting point if these tools are meant to shape policy and frontline services.

And while ministers like to say AI will "liberate" staff from admin, in practice, once 28,000 people get used to it drafting and summarizing, it's not something you just switch off.

Which leaves HMRC with a familiar problem: a system that works well enough to rely on, not quite well enough to trust, and far too embedded to switch off when it inevitably gets something important wrong. ®