HMRC say they are investigating the reasons why they issued incorrect 2013/14 P800 tax calculations and payable orders to unknown thousands of PAYE taxpayers.

The department has laid blame on employers following a bulk end-of-year reconciliation exercise that saw erroneous information sent over a three-week period starting on 15 September. But tax experts claim deficiencies of the Revenue’s systems were at least partially responsible.

Incorrect overpayments and underpayments were show where pay and tax shown does not match that shown on 2013/14 P60, said the Revenue. “We currently do not know the scale of the issue, but some …