Vulnerable and elderly people are being told they owe large amounts of tax which they can only pay off through digital vouchers and gift cards.
HMRC has issued a warning over fraudsters who are preying on victims by cold-calling them and impersonating members of staff from the Revenue.
Figures from Action Fraud, the national fraud reporting centre, show there have been more than 1,500 reports of this scam between January 2016 and August 2017.
The numbers have increased in recent months, with the vast majority of victims being over the age of 65 and suffering an average financial loss of £1,150.
The Revenue, which labelled the scammers as "very confident, convincing and utterly ruthless", insists it would never use this method of payment to process a tax bill.
Angela MacDonald, HMRC's director-general of customer services, said:
"We urge people to warn elderly relatives about this scam and remind them that they should never trust anyone who phones out of the blue and asks them to pay a tax bill.
"If you think you've been a victim you should contact Action Fraud immediately."
If you or a vulnerable relative have been targeted by this scam or con artists in general, you should report it immediately to Action Fraud on 0300 123 2040.