Over 31,000 individuals submitted their 2020/21 tax return between Christmas Eve and Boxing Day, HMRC has said.
That includes 2,828 people who submitted their tax return on Christmas Day, the peak time for filing being 12:00 to 12:59, when HMRC received 227 returns.
An additional 19,802 individuals completed their self-assessment on Christmas Eve, while 8,641 did theirs on Boxing Day.
Myrtle Lloyd, director-general for customer services at HMRC, said:
"Filling in a tax return won't have been on many people's to-do lists for Christmas, but please don't leave it until the end of January either.
"We have videos, guidance and helpsheets to support you - just search ‘self-assessment' on GOV.UK to find out more."
The deadline for filing a self-assessment tax return for the 2020/21 tax year is 31 January 2021, which is also when the tax is due.
Talk to us for assistance with your self-assessment tax return.