With less than a month to go, 5.4m taxpayers still need to complete and pay their tax self-assessment and avoid penalties, HMRC has warned.

On New Year’s Day 28,400 keen form fillers filed their returns, according to new HMRC figures published today.

On New Year’s Eve some 38,260 filed their returns, with 310 filing between 11pm and midnight.

Anyone required to file a tax return for the 2023 to 2024 tax year who misses the 31 January deadline could face an initial late filing penalty of £100.

Myrtle Lloyd, HMRC’s director general for customer services, said: “We know completing your tax return isn’t the most exciting item on your New Year to-do list, but it’s important to file and pay on time to avoid penalties or being charged interest.”

He said the quickest and easiest way to complete a tax return was to use HMRC’s online services.

Some 97% of taxpayers now file online, HMRC said.

For people unable to meet the tax return deadline, HMRC said it will treat those with reasonable excuses fairly if they tell the tax collection body before 31 January.

The penalties for late tax returns are:

• an initial £100 fixed penalty, which applies even if there is no tax to pay, or if the tax due is paid on time
• after 3 months, additional daily penalties of £10 per day, up to a maximum of £900
• after 6 months, a further penalty of 5% of the tax due or £300, whichever is greater
• after 12 months, another 5% or £300 charge, whichever is greater

There are also additional penalties for paying late of 5% of the tax unpaid at 30 days, 6 months and 12 months.

If tax remains unpaid after the deadline, interest will also be charged on the amount owed, in addition to the penalties above.