Despite last minute calls to push back the deadline, a record number of self-assessment tax returns were filed before midnight on January 31st.

In total, HM Revenue & Customs received 10.3 million tax returns for 2012/13, beating the previous year’s total of 9.61 million.

Much of the increase was down to the Government’s controversial changes to the child benefit system, which meant thousands of high-earning parents were required to complete a self-assessment tax return.

With many doing so for the first time, one of the UK’s accountancy bodies, The Association of Chartered Accountants (ACCA), called upon HMRC to ‘do the right thing’ and extend the self-assessment deadline until February 3rd .

Despite some taxpayers being granted an eleventh-hour reprieve in the form of a 2 week extension, the January deadline remained in place for the vast majority.

The busiest day for online tax returns was in fact ‘deadline day’, when more than half a million (569,847) taxpayers scrambled to submit before midnight. Between 4pm and 5pm, more than 12 tax returns were submitted every second.

Although a record-breaking number filed their return on time, around 700,000 Brits did not, meaning they have fallen victim to HMRC’s £100 late filing penalty.

Tardy taxpayers are now subject to a £10 fine for each day that their tax return remains outstanding, up to a maximum of £900.

The number of taxpayers required to submit a self-assessment tax return has soared in recent years. Just 1.4 million people filed a tax return for the 2006/07 tax year, compared to over 10 million today.