The increase has raised concerns among accountants that HMRC may be treating some mistakes as evasion

Middle-class taxpayers have been issued with a record number of fines for making mistakes on their returns.

HM Revenue & Customs imposed 143,000 penalties last year on people who filed inaccurate information because it deemed them not to have taken “reasonable care” — nearly three times the 55,000 fines levied in 2012.

Accountants warned yesterday that people were being penalised for forgetting to declare the interest on a long-lost savings account or omitting a health insurance policy or gym membership received through work.

The figures emerged as HMRC’s phoneline descended into chaos before today’s deadline for online returns. A technology failure left callers uncertain whether tax payments had cleared because they were cut off before getting a transaction number. HMRC apologised and said that no