Around 8.5 million tax returns have been submitted ahead of the 31 January deadline.

But HM Revenue & Customs (HMRC) is urging those with outstanding returns to get them in as soon as possible to avoid hefty fines.

Jesse Norman, financial secretary to the Treasury, said: “The deadline is fast approaching for more than three million taxpayers who have not yet managed to file their tax returns. With only one week until 31 January, HMRC strongly encourages people to file their Self-Assessment.

“Anyone who believes they might not be able to file on time should make sure to call or email HMRC.”

Angela MacDonald, HMRC director general of customer services, said: “We’re here to help customers get their tax right, and have put in place a range of help from online services, webinars and videos, to customer service helplines, webchats and social media channels.

“We know completing a tax return can be confusing at times, so please do get in touch if you’re still concerned about how to file, or about paying what you owe. HMRC colleagues are standing by to provide support and advice ahead of the deadline.”

If you’re completing a tax return for the first time, have yet to start or need help, HMRC provides a self-assessment video to view, plus there are guides on the Gov.uk site. You can also call the self-assessment helpline on 0300 200 3310 or contact HMRC via social media (don’t disclose any personal information though).