Nearly 6 million people will be informed over the coming months that they have paid the wrong amount of tax, with about 1.4 million facing demands for more payments, it has been revealed.
A total of £2 billion has been underpaid through the Pay as You Earn (PAYE) system over the past two years, meaning that the 1.4 million taxpayers will be required to shell out an average of almost £1,500 each.
Meanwhile, 4.3 million people will have better news, with the taxman telling them that they have paid too much.
With a total overpayment of £1.8 billion, each could receive an average rebate of £418.
The first 45,000 letters from HM Revenue and Customs are expected to arrive on doormats on Tuesday.