The government has issued a warning to people who complete a self-assessment tax return to be alert to criminals claiming to be from HMRC.

The annual tax return deadline is on 31 January and HMRC issues thousands of text messages and emails to remind people to file their tax returns.

But fraudsters also use calls, emails and texts to contact customers. In the past 12 months, HMRC has responded to more than 846,000 referrals of suspicious HMRC contact from the public, and reported more than 15,500 malicious web pages to internet service providers to be taken down.

Many scams target customers to inform them of a fake ‘tax rebate’ or ‘tax refund’ they are due. The imposters use language intended to convince them to hand over personal information, including bank details, in order to claim the ‘refund’.

If this information is handed over, criminals use it to access customers’ bank accounts or trick them into paying fictitious tax bills. In some cases they sell on people’s data to other criminals.

Karl Khan, HMRC’s interim director general for customer services, said: “We know that criminals take advantage of the self-assessment deadline to panic customers into sharing their personal or financial details and even paying bogus ‘tax due’.

“If someone calls, emails or texts claiming to be from HMRC, offering financial help or asking for money, it might be a scam. Please take a moment to think before parting with any private information or money.”

Pauline Smith, head of Action Fraud, said: “Criminals are experts at impersonating organisations that we know and trust. We work closely with HMRC to raise awareness of current scams and encourage people to report any suspicious calls or messages they receive, even if they haven’t acted on them, to the relevant channels.

“This information is crucial in disrupting criminal activity and is already helping HMRC take down fraudulent websites being used to facilitate fraud.”

“It’s important to remember if you’re contacted out the blue by someone purporting to be from HMRC asking for your personal or financial details, or offering you a tax rebate, grant or refund, this could be a scam.

“Do not respond, hang up the phone, and take care not to click on any links in unexpected emails or text messages. You should contact HMRC directly using a phone number you’ve used before to check if the communication you have received is genuine.”

Customers can report suspicious activity to HMRC at phishing@hmrc.gov.uk or by sending a text to 60599. They can also report phone scams online on GOV.UK.