The taxman has stressed that it would be contacting all affected customers and that they would suffer no financial loss.
Criminals have successfully stolen £47 million from HMRC, a Treasury committee has been told.
As part of the attack, the tax authority “detected activity” on the PAYE accounts of roughly 100,000 taxpayers.
John-Paul Marks, chief executive of HMRC, told the committee yesterday that those affected would be notified and that they would not lose money as a result.
“It’s about 0.2% of the PAYE population, around 100,000 people, who we have written to, are writing to, to notify them that we detected activity on their PAYE account.”
He added: “To be clear, no financial loss to those individuals.”
Scammers steal £47m from HMRC
The criminals have been fraudulently claiming money from HMRC rather than targeting the affected taxpayers directly.
As part of the conversation with the committee yesterday, Angela MacDonald, deputy chief executive at HMRC, revealed the criminals had succeeded in stealing millions of pounds.
“At the moment, they’ve managed to extract repayments to the tune of £47 million,” she said.
“Now that is a lot of money, and it’s very unacceptable.
“Overall, in the last tax year, we actually protected £1.9 billion worth of money which sought to be taken from us by attacks.”
Are affected taxpayers safe?
The tax authority revealed that it has locked down affected accounts and deleted login details to prevent future unauthorised access.
Any incorrect information has also been deleted from tax records, and there were checks to ensure no other details were changed.
As mentioned earlier, HMRC will also write to all those affected to explain what has happened, with letters expected to arrive in the next three weeks.
An HMRC spokesperson said: “We’ve acted to protect customers after identifying attempts to access a very small minority of tax accounts, and we’re working with other law enforcement agencies both in the UK and overseas to bring those responsible to justice.
“This was not a cyber-attack – it involved criminals using personal information from phishing activity or data obtained elsewhere to try to claim money from HMRC.
“We’re writing to those customers affected to reassure them we’ve secured their accounts and that they haven’t lost any money.”