If you’ve not completed your tax return yet (or your accountant for that matter) then you must do it online by the end of the month to avoid a penalty.
You must send your online tax return by midnight on Sunday 31 January 2010. The deadline is only later than this if it was after 31 October when HM Revenue & Customs (HMRC) asked you to complete a return – see the section ‘Tax return or ‘Notice to file’ received after 31 October’ on the website
There’s a very small number of cases where HMRC will still allow you to send your tax return on paper – see the section ‘Exceptions – where you can’t file online’ below.
If HMRC receive your tax return after 31 January you’ll get a late filing penalty of £100,
Does tax have to be taxing?
For more information visit: http://www.hmrc.gov.uk/index.htm