The taxman has dropped a warning that up to a million Brits could be missing out on unclaimed tax refunds worth an average £453 each. And it has emerged that hundreds of thousands risk missing out simply because they have not checked their accounts.

In a brief post on X this week, HM Revenue & Customs (HMRC) said that roughly one million taxpayers have not yet claimed money they are owed from overpaid tax – often because they never checked whether they were due a refund. That could leave ordinary workers and pensioners thousands of pounds out of pocket if they don’t act fast, the government body said.

The typical amount owed to these taxpayers comes out at about £453 per person, according to the official alert, with many overpayments caused by simple mistakes such as being put on the wrong tax code, changing jobs, or retiring without updating HMRC’s records.

HMRC stressed that you will not get this money automatically – claimants must check their personal tax account on GOV.UK or the HMRC app and submit a claim.

Officials have also warned that scammers are exploiting the situation by sending bogus texts, emails or calls claiming taxpayers are due refunds in a bid to steal personal and banking data. More than 135,000 HMRC‑related scam reports have been logged recently, including about 29,000 involving fake tax refund claims, and the number of fraudulent approaches continues to rise.

Lucy Pike, HMRC’s Chief Security Officer, said: “Millions of people file a tax return each year and scammers mimic HMRC to try and catch unsuspecting victims out.

“I’m urging people to stay vigilant and if any emails, text messages or phone calls appear suspicious – don’t be lured into clicking on links or sharing your personal information – report it directly to HMRC.”

Experts say thousands are leaving cash on the table simply by ignoring letters or failing to set up online tax accounts – and with scammers circling, the danger of handing over cash to fraudsters is high.

Genuine tax refunds will be notified through HMRC’s secure system or by post – the department will never ask for bank or personal details via an unsolicited email or text.

Advisers are urging taxpayers to log into their accounts today – before it’s too late and the unpaid refunds slip into the long grass.