HMRC has estimated that around a million people failed to meet the 31 January 2026 Self Assessment tax return filing deadline.

It reported that 11.48 million taxpayers submitted their returns on time, with the majority filing online. As expected, there was a surge in submissions on the deadline day itself, with nearly half a million returns filed on 31 January. This included more than 27,000 submissions made in the final hour before midnight. The busiest period was between 5 pm and 6 pm, when almost 33,000 tax returns were filed.

Despite this last-minute rush, HMRC believes that around a million people missed the deadline altogether.

If you missed the deadline

If you have not yet filed your tax return, it is important to do so as soon as possible. HMRC charges an immediate £100 late filing penalty, even where no tax is due.

Additional penalties apply depending on how long the return remains outstanding:

  • After three months: £10 per day (up to £900).

  • After six months: 5% of the tax due or £300, whichever is higher.

  • After 12 months: a further 5% or £300.

There are also penalties for late payment of tax. These are charged at 5% of any unpaid balance after 30 days, six months and 12 months, in addition to interest.

If you need support with filing your tax return, please get in touch. We would be happy to help.

What’s coming next

Making Tax Digital for Income Tax will begin from April 2026 for many sole traders and landlords.

From 6 April 2026, Making Tax Digital (MTD) for Income Tax will be mandatory for sole traders and landlords with qualifying income over £50,000. Under MTD, taxpayers will need to keep digital records and submit quarterly updates to HMRC.

If you would like help preparing for MTD, please contact us. We can support you with every aspect of the process, including selecting suitable software, bookkeeping, and submitting quarterly updates and the end of year return.

See: https://www.gov.uk/government/news/1148-million-beat-the-self-assessment-deadline