People find filling in forms a chore. None more so than the self-assessment tax returns due in by the end of this month.

There’s not much time left - and none if you happen to fill it in wrong and it has to be returned, meaning an automatic £100 fine.

Roy Massingale, director of self-assessment at HM Revenue & Customs said, "We know people find the process a chore. We are highlighting some of the most common mistakes, so when people send us their return they get it right first time."

When processing tax returns, HM Revenue & Customs has found the ten most common mistakes are:

• A 'yes' tick has been entered in one of the questions 1 to 9 on page 2 of the tax return but the supplementary page has not been forwarded with the tax return.
• Failure to complete the self-employed pages, particularly on page SE3 from box 3.74 onwards.
• Detailing information on separate schedules instead of including the information on the return.
• Entering manuscript notes on the return i.e. "per accounts" and/or "information to follow" instead of entering actual figures on the form.
• Failure to complete a separate supplementary page for each individual employment.
• Entering the net figure of employee personal pension premiums instead of the gross figure at box 14.11 of the core return (i.e. claiming insufficient relief where higher rates of tax are payable).
• Entering the figure of capital expenditure in Box 3.14 of the Self Employment pages instead of the figure of capital allowances (i.e. claiming excessive relief).
• Failure to complete question 19 of the core return where a repayment is due. We will assume you wish to leave the overpaid amount on your record, to be set against future liabilities - you have the right to choose.
• Entering your pay in box 1.8 but not entering any tax deducted in box 1.11 on the Employment pages.
• And most importantly.....!
  If you fail to sign the return, it will be rejected immediately.

People needing help or more information can visit http://www.hmrc.gov.uk or telephone the self assessment helpline on 0845 900 0444. The helpline is open 8am-8pm seven days a week.