If you still haven’t sent your HM Revenue & Customers tax return for the year to 5 April 2013 you could incur payment penalties. If you are sending online you can check you have fully submitted it by checking your online account, ‘tax return options page’ and find the date of the receipt. Remember you must pay everything you owe by 31 January 2014.
The paper deadline was 31st October 2013 so your only option now is for online tax return, if you’re late you will automatically be charged £100, even if you’ve no tax to pay or have already paid what you owe. If by 30 April 2014 you have still not sent your online tax return you will incur a further £10 daily penalty for every day it remains outstanding up to a maximum £900 after 90 days, starting 1 May 2014 for online returns (or 1 February 2014 for paper tax returns).