More than 10.2 million people filed their self-assessment online by the 31 January deadline this year, leaving approximately 2.3m yet to file.
Although no penalties will be imposed on late filers as long as they file by 28 February 2022, they do face interest charges at 2.75% on the tax they owe, which will increase over time.
Last month, HMRC announced no penalties would be levied throughout February to alleviate pressure on individuals and tax advisers to beat the original deadline for online submissions.
From 1 March 2022, the regular penalty system will apply, which sees late filers pay an instant £100 fine.
Myrtle Lloyd, director general for customer services at HMRC thanked the "millions of customers and agents who sent us their tax return and paid in time for this week's deadline".
She added:
"Customers can set up a monthly payment plan online if they're worried about paying their tax bill. Search ‘Self Assessment' on GOV.UK to find out more."
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