Nearly a million taxpayers missed last week's 2018/19 self-assessment deadline, according to HMRC.
Official statistics showed, however, that a record 11,122,967 taxpayers out of 11.7m beat the midnight self-assessment deadline on 31 January 2020.
Those with more than one source of income and sole traders who earned more than £1,000 needed to complete tax returns for 2018/19.
A record 10.4m taxpayers filed their returns online, with the remainder getting their returns in before the paper deadline on 31 October 2019.
Some 702,171 tax returns were sent in on deadline day, and the peak filing hour was from 4pm to 5pm when 56,969 returns were filed.
Amazingly, 26,562 people filed their returns less than an hour before the deadline.
Angela MacDonald, director-general for customer services at HMRC, said:
"It's great to see that the majority of customers have submitted and paid their tax returns before 31 January.
"I'd like to thank everyone who filed and paid on time, but anyone yet to file or pay should contact HMRC straight away because we are here to help."
The 958,296 taxpayers who missed last week's deadline increased from 731,186 on the previous year, when 10,833,177 returns were due.
HMRC can demand penalties of £100 for late filing during the first three months after missing the deadline, after which additional fines can apply.
We can handle your tax returns.