Individuals could be paying more tax later this year after HM Revenue and Customs (HMRC) sent out incorrect tax codes, experts have claimed.

The Chartered Institute of Taxation (CIOT) has warned that the introduction of HMRC’s new computer system could result in ‘huge numbers of people’ being issued the wrong information.

In the worst cases, the organisation estimates that taxpayers could be asked to pay up to £108 extra a month. With around 25 million tax codes sent out ahead of the new tax year, the CIOT is urging the Revenue to do more to alert people to the potential problem.

‘Most people on PAYE are used to assuming that what the taxman sends them is correct,’ said the CIOT’s Andrew Hubbard. ‘But this year, many of them are being given wrong information, and unless they spot it and tell HMRC, their employer will receive the wrong information too.

‘They could get a nasty shock when they open their April pay packet and see it is as much as a hundred pounds lighter than they are expecting,’ he added.

HMRC’s new computer system combines information on National Insurance and PAYE for the first time. Whilst the CIOT has highlighted flaws in the system, the Revenue insists the new process ‘is improving the accuracy of the PAYE so that more people than ever before are correctly taxed’.

‘There will be some incorrect tax codes as there always are at this time of year,’ said a HMRC spokesman. ‘But the coding notice tells people what the code relates to and tells them to contact us if it is wrong’.