by Trevor Sturgess

The last Sunday in January will be no day of rest for taxpayers who have not filed their online return by then.

HM Revenue and Customs is not expected to show any leniency to people using Sunday as an excuse for missing the January 31 deadline.

Miss it by so much as a minute and you could face a £100 fine.

The Institute of Chartered Accountants in England and Wales (ICAEW) warns taxpayers that they will still be liable for a fine by if they fail to submit their self assessment online by January 31, even though it’s a Sunday this year. More than 5.8 million people - last year’s figure - are expected to file online.

Anita Monteith, technical manager from the ICAEW tax faculty, said: “Do not think that just because the deadline falls on a Sunday, HMRC will not be strict in handing out fines to those who file late. Even if you file your return in the early hours of Monday February 1, you will still be liable to a £100 penalty.

“Don’t treat Sunday, January 31, as a day off if you haven’t already filed and make sure you do so before the midnight deadline.”

HMRC expects more than nine million people - nearly 250,000 in Kent - to file a Self Assessment tax return this year, well up on the 5.8 million last year, and 3.8m in 2007. People who submit a paper return also face a £100 penalty because the paper filing deadline passed on October 31.

HMRC's Sarah Walker said: "If you haven't yet sent in your 2008-09 tax return, you need to start thinking about it now. And if you haven't filed online before, allow plenty of time to complete the registration process - that way, you'll avoid a last-minute rush at the end of the month."

The ICAEW says that if taxpayers follow its guidelines, they will avoid a stressful weekend at the end of January.

• Register online if you have not already done so. It can take up to seven days for you to receive the activation code which HMRC will send to you in the post.
• Check if you need to complete a return. If you haven’t been told you need to do a self assessment tax return but have a new source of income or capital gains in 2008/09 on which you need to pay tax you will still need to complete a form.
• Get your paperwork together.
• You can fill in the form in stages. You don’t have to do the whole process in one go. The information on screen can be saved as you go along allowing you to continue at another time.
• Check the form for errors. An online form that is not completed correctly can be rejected.
• Compare the return with the previous year’s return. If there are any significant changes explain why on the form.
• Save a copy of the form and print a copy of the receipt you receive when you submit it

Records of all information used to complete tax returns must be kept for 22 months after the end of the tax year or for five years and 10 months for those with a business or who have income from letting out property. There is a minimum penalty of up to £3,000 for each tax year for which records have not been kept

Don’t leave it until the last minute.