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Self Assessment deadline 31 January 2027: what's due, and what it costs if you're late

By Paul · Last checked against GOV.UK on · How we check facts

If you're self-employed or a landlord, the big date this winter is 31 January 2027. By 11:59pm that day HMRC needs two things from you. Your online tax return for 2025 to 2026, and any tax you owe for it.

This year the return matters a bit more than usual. The turnover on it is what HMRC uses to decide if you join Making Tax Digital in April 2027.

What's due by 31 January 2027

  • Your online return for 2025 to 2026. That's the tax year 6 April 2025 to 5 April 2026. The paper deadline was 31 October 2026, so it's online only now. (Self Assessment deadlines, GOV.UK)
  • Any tax you still owe for 2025 to 2026. This is called the "balancing payment". (Payments on account, GOV.UK)
  • Your first payment on account for 2026 to 2027, if you have to make them. Each one is usually half of last year's tax bill. The second is due by 31 July 2027. You don't need to make them if last year's bill was under £1,000, or if more than 80% of your tax was already taken another way, for example through your tax code. (Payments on account, GOV.UK)

If it's your first year in Self Assessment and you have to make payments on account, that January bill can be bigger than you expect. It's the year's tax plus half of it again, as the first payment towards next year.

Two other dates to know

  • 30 December 2026. If you also have a job or a pension that pays through PAYE, and you owe less than £3,000, HMRC can collect the tax through your tax code instead. For that, your online return has to be in by 11:59pm on 30 December 2026. (Pay through your tax code, GOV.UK)
  • If you registered for Self Assessment after 5 October 2026, HMRC gives you a different deadline for the return. It's 3 months from the date on its letter or email. The tax still has to be paid by 11:59pm on 31 January 2027. If you registered late and don't pay it all by then, you may also get a "failure to notify" penalty. (Deadlines and Penalties, GOV.UK)

What it costs if you're late

Late return:

  • £100 to start with.
  • After 3 months, £10 a day, up to £900.
  • After 6 months, another 5% of the tax due or £300, whichever is more.
  • After 12 months, another 5% or £300 again.

Late payment:

  • 5% of the unpaid tax at 30 days.
  • Another 5% at 6 months, and again at 12 months.
  • You're charged interest on what you owe as well.

Source: Self Assessment penalties, GOV.UK

So a return that's a day late costs £100. The longer it's left, the more it adds up. If you think you've got a reasonable excuse, you can appeal.

If you're already using MTD

If you joined MTD for Income Tax in April 2026, the penalties above still apply to this return. HMRC gives this exact example: "if you use Making Tax Digital for Income Tax from 6 April 2026, current penalties will apply to your 2025 to 2026 tax return deadline of 31 January 2027". The new points system starts from the year you joined MTD.

Source: Penalties for MTD for Income Tax, GOV.UK

Why this return decides your MTD start date

HMRC checks your qualifying income on this return. That's your self-employment and property income added together, before expenses. If it's over £30,000, you'll need to use MTD for Income Tax from 6 April 2027. HMRC says it will write to you if so, but it's still up to you to check.

It's turnover, not profit. Say a plumber took £34,000 and spent £12,000 on parts. Their qualifying income is £34,000. Wages from a job don't count, and neither do pensions or dividends.

Sources: Find out if and when you need to use MTD for Income Tax and Work out your qualifying income, GOV.UK

If you do join in April 2027, your first quarterly update is due by 7 August 2027. (Send quarterly updates, GOV.UK)

Not sure where you stand? Put your numbers in the free MTD checker. It takes a minute and nothing you type leaves your browser.

Can't pay in full?

Send the return on time anyway. The late filing penalty is separate from the tax, so filing on time keeps that part off your bill. Then look at paying in instalments. HMRC can set up a payment plan if it's affordable for you: If you cannot pay your tax bill on time, GOV.UK.

A simple plan for the next few weeks

  1. Find your HMRC sign-in details now. Don't leave it to the last week.
  2. Get your 2025 to 2026 totals together: money in, costs out, and any rent.
  3. File early if you can. You still don't have to pay until 31 January.
  4. Write down your turnover figure. If it's over £30,000, have a look at MTD software.

Sources

We checked each of these on GOV.UK on 3 November 2026. If HMRC changes them, this page will change too.

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This page is general information, not tax advice. Read why. Page history: 3 November 2026, full check against GOV.UK.

Drafts are sometimes prepared with help from AI writing tools. Every fact is checked against the GOV.UK page it links to, and Paul reads and approves each page before it goes up. How we check facts.

Quotes and facts from GOV.UK: contains public sector information licensed under the Open Government Licence v3.0. Quoted words are HMRC's or HM Treasury's, not ours.