Londoners are more likely to miss their tax return deadline than people living in any other part of the UK, according to HM Revenue and Customs figures.
Around one in nine (11%) of the 560,000 people in inner London who had to send in a tax return last year failed to do so by the relevant deadlines of October 31 for paper returns and January 31 for online submissions.
The one million taxpayers in outer London were more punctual, with one in 11 (9%) failing to meet the deadline, but they were still the second worst offenders, HMRC said.
The tardiest taxpayers outside of London were in the North West of England, with 8% of their 890,000 returns failing to meet the deadline.
The most punctual taxpayers live in the South West, with only 6% of their one million tax returns arriving late last year. The other English regions, as well as Wales, Scotland and Northern Ireland, all registered 7% of late tax returns, which was in line with the UK average.
Around 10.9 million people are expected send a tax return for the 2012-13 tax year and more than 3.5 million returns are still due to be received before the January 31 deadline.
Households where one parent earns over £50,000 a year who continued to receive child benefit after January 7 2013 have to pay a tax charge. If one parent has a taxable income of more than £60,000, then they must pay all the money back.
Parents who have neither registered for self-assessment nor opted out altogether must register for self-assessment now. Online registration can take up to seven working days to complete as an activation code has to be sent out in the post.
HMRC director general of personal tax, Ruth Owen, said: "Whether you're from London, Livingston, Lisburn or Llandudno, the consequences of missing the tax return deadline are the same - an automatic £100 late-filing penalty.
"The longer you delay, the more you have to pay. So if you still have to send us your tax return, take action now."