Revenue and Customs says it doesn't know why a number of penalty notices were mistakenly issued to employers that correctly returned their P11D(b) forms.

The charges were sent to companies that submitted their 2007-08 return of Class 1A National Insurance contributions online and on time.

However, an apologetic HMRC said that it is unsure of the scale of the problem or how it happened.

“There is no question of anyone having to pay a penalty if their return was filled in on time,” added a HMRC spokesman.

The penalty charge is £100 per 50 employees for each month the return is late and should only be issued to companies that returned forms on July 7 or later.

“The penalty notice tells people what to do if they do not know why they have received a penalty notice,” said the HMRC spokesman.

“We are urgently looking into this and will issue more detailed information as soon as we can.”

Companies that sent in their P11D(b) forms before July 6, 2008, and have received a penalty charge can contact the employer helpline on 08457 143 143.

If you've incorrectly received a penalty notice please let us know by posting your comments below.