The tax system in use by HM Revenue & Customs (HMRC) is complex and causes problems for employers, employees and contractors, it has been said.

According to the Association of Chartered Certified Accountants (ACCA), many taxpayers are worried that mistakes made by HMRC are costing them.

"While it is important we pay the right amount of tax at the right time, it is also important that our tax authority bills us correctly and keeps correct records," said Craig Vickery, head of ACCA Scotland.

"This issue highlights the problems caused by the complexity of the UK's tax system."

He suggested that millions of pounds are owed to those who file their own tax returns, such as IT contractors, because of errors in the self assessment system.

Millions of people have underpaid and are set to receive demands from HMRC, while millions more have paid too much and could be due a rebate.