HMRC rushed out an apologetic statement from the senior civil servant.
"I am deeply sorry that people are facing an unexpected tax bill," Mr Hartnett said.
"Everyone in HMRC is working hard to make this as painless as possible. I apologise if my remarks came across as insensitive. I am working flat out with my colleagues to ensure everyone's tax is correct and the new computer system will help us do this.
"It was this new system that revealed the extent and size of reconciliations required and will help us be more accurate in future but we do not underestimate the distress caused to taxpayers and once again I apologise."
Just one day earlier, it was completely fucking different:
Dave Hartnett, the country's top tax official, has refused to apologise to 1.4 million people facing demands for extra money – adding that the situation was not "extraordinary".
Asked if he would say sorry to those facing unexpected bills, Mr Hartnett told BBC Radio 4's Money Box programme: "I'm not sure I see a need to apologise.
"I've read the papers, listened to the media and heard stories of HMRC blunder and IT failure – neither of those are true.
ONLY 1.4 million people? ONLY?
Why is this MOTHERFUCKING CUNT allowed to get away with a fucking apology? Why is his fucking barefaced arrogance not just kicked the fucking fuck out of his overpaid, clearly fucking unaccountable job? Why am I contributing towards his fucking salary?