Millions of taxpayers have less than a month left to file their Self Assessment tax return, according to new figures from HMRC.
With the 31 January deadline fast approaching, 5.65 million people are still yet to submit their return for the 2024/25 tax year, despite a surge of filings over the New Year period. HMRC said more than 54,000 customers chose to see in 2026 by completing their tax return on New Year’s Eve and New Year’s Day.
In total, 6.36 million taxpayers have already filed, meaning more than half of the expected 12 million Self Assessment customers now have their tax affairs in order.
HMRC’s data shows that 342 customers filed in the final hour of 2025, while nearly 20,000 people spent New Year’s Day submitting their return instead of taking a walk or watching TV. The busiest filing hour across the two days was between 11am and 11.59am on 31 December.
Myrtle Lloyd, HMRC’s chief customer officer, urged those who have not yet started to act quickly.
“New Year is a great time to start afresh. What better way than to ensure your tax affairs are in order for another year than completing your tax return,” she said.
Those who miss the cut-off face an automatic £100 late filing penalty, even if no tax is owed. Additional daily penalties apply after three months, followed by further charges at six and 12 months, alongside interest on any unpaid tax.
A Self Assessment tax return must be completed by anyone who, in the last tax year was self-employed as a sole trader and earned more than £1,000 before expenses, was a partner in a business partnership, had to pay Capital Gains Tax after selling or disposing of an asset, or was liable for the High Income Child Benefit Charge and does not pay it through PAYE.
A return may also be required for those with untaxed income, including money from renting out a property, tips or commission, income from savings, investments or dividends, and foreign income.
HMRC highlighted that customers can complete their return online, save progress and return to it later. While the tax bill does not have to be paid immediately after submission, it must be settled by 31 January. The easiest way to pay is via the HMRC app, which also allows users to set up payment reminders.
The tax authority also reminded customers that anyone unable to meet the deadline should contact HMRC before 31 January, as those with a reasonable excuse will be treated fairly.
Looking ahead, HMRC flagged an important change for many small business owners. From 6 April 2026, sole traders and landlords with a turnover above £50,000 will be required to use Making Tax Digital for Income Tax, submitting quarterly updates of income and expenses. Eligible customers are being encouraged to sign up early to allow time to choose software and prepare for the new system.
HMRC also warned Self Assessment customers to remain alert to scams, stressing that taxpayers should never share their HMRC login details, even with a tax agent.