Key takeaways

  • If you miss the 31 January 2027 online deadline, HMRC charges a £100 late filing penalty straight away, even if you owe no tax.
  • File as soon as you can: if the return is still missing on 1 May 2027, HMRC adds £10 a day for up to 90 days, a maximum of £900.
  • Interest runs on unpaid tax from 1 February 2027 at HMRC's late payment rate, which is 8.00% from 24 November 2026.
  • Tax still unpaid at the end of 2 March 2027 gets a 5% late payment penalty, so paying before then avoids it.
  • You can set up a Self Assessment payment plan online if you owe £30,000 or less, your returns are up to date and you have no other HMRC debts or plans.
  • If you had a reasonable excuse, such as an unexpected hospital stay, you can appeal online or on form SA370, usually within 30 days of the penalty notice.
  • The Self Assessment payment problems line is 0300 200 3820, open Monday to Friday, 8am to 6pm.

If you missed the 31 January 2027 deadline for your 2025 to 2026 tax return, file it online as soon as you can. HMRC’s £100 penalty is already due, but filing before 1 May 2027 stops the £10 daily penalties, and paying before the end of 2 March 2027 avoids the first 5% late payment penalty. If you cannot pay in full, set up a payment plan, and if something serious stopped you filing, appeal.

What happens if you miss the 31 January deadline?

HMRC charges an automatic £100 late filing penalty if your online return arrives after 11:59pm on 31 January 2027. GOV.UK’s penalties page says the £100 applies even if you have no tax to pay or have already paid.

Missing the deadline does not stop you filing. HMRC’s online service stays open, and you file the same way you would have before the deadline.

How much will it cost?

The cost depends on how long the return stays unfiled and how long the tax stays unpaid. These are the late filing penalties for a 2025 to 2026 return.

Return still not filedFromPenalty
1 day late1 February 2027£100
3 months late1 May 2027£10 a day, up to £900
6 months late1 August 20275% of tax due or £300
12 months late1 February 20285% of tax due or £300

Late payment is charged separately. You pay 5% of the tax still unpaid at the end of 2 March 2027, again at 2 August 2027 and again at 2 February 2028, following the 30-day, 6-month and 12-month triggers in HMRC’s Self Assessment Manual.

Interest also runs from 1 February 2027. HMRC’s interest rates page, updated 6 November 2026, sets the late payment rate at 8.00% from 24 November 2026. The rate moves with Bank Rate, so check it when you pay. For the full timeline, see Self Assessment late filing penalties.

What should you do first?

File first, then deal with the bill. Follow these steps in order.

  1. Find your UTR and log in. Your 10-digit Unique Taxpayer Reference is on HMRC letters and your online account. Our guide on how to find your UTR shows where.
  2. File the return online. Use HMRC’s service or your software. Our step-by-step filing guide covers each section.
  3. Note the amount due. The calculation shows the balancing payment and any first payment on account for 2026 to 2027, both due 31 January 2027.
  4. Pay what you can now. Every payment cuts the interest and the tax exposed to the 5% penalty on 2 March 2027.
  5. Set up a plan for the rest. Do this before 2 March 2027 if you can.
  6. Check the penalty notice when it arrives. Appeal within the time it gives if you had a reasonable excuse.

GOV.UK’s penalty estimator gives a rough figure for penalties and interest. It does not account for payments you have already made or earlier years’ balances.

What if you cannot pay the bill?

You can spread the bill with a payment plan, known as Time to Pay. HMRC’s online payment plan service says you can set one up yourself if you:

  • are up to date with your tax returns
  • owe £30,000 or less
  • have no other tax debts
  • have no other HMRC payment plans

Payments are taken by Direct Debit. Interest is still charged on the balance until it is paid. If you do not qualify online, call the Self Assessment payment problems line on 0300 200 3820, Monday to Friday, 8am to 6pm. HMRC expects you to use savings or assets to reduce the debt. Read more in our guide to HMRC Time to Pay.

Can you appeal the penalty?

Yes, if you had a reasonable excuse for missing the deadline. GOV.UK’s reasonable excuses page lists examples HMRC may accept, and ones it will not.

  • May be accepted: your computer or software failed while you were preparing the return; an unexpected hospital stay; postal delays you could not have predicted.
  • Will not be accepted: you found HMRC’s online system too difficult; you did not get a reminder; you made a mistake on the return.

You must file as soon as the excuse ends. You usually have 30 days from the date of the penalty notice to appeal, online or by post on form SA370. Have the penalty date, the filing and payment dates and details of your excuse ready. Our guide to what HMRC accepts as a reasonable excuse has more examples.

Which applies to you?

  • If you file and pay in full in February 2027, you pay £100 plus a small amount of interest.
  • If you file in February but cannot pay, set up a plan before 2 March 2027 and keep to it.
  • If you registered after 5 October 2026, your filing deadline is 3 months from the date on HMRC’s letter or email, so you may not be late at all; the tax was still due 31 January 2027.
  • If you never registered, register now; a failure to notify penalty may apply instead.
  • If you had a serious illness or a bereavement, file when you can and appeal the penalty.

Do the new penalty points apply?

No. The points-based late filing system applies to personal Self Assessment returns from April 2027, so a 2025 to 2026 return is charged under the rules above. Our explainer on HMRC penalty points covers the new system.

Frequently asked questions

Can I still file my tax return after 31 January?

Yes. HMRC’s online service stays open after the deadline. File as soon as possible to stop further penalties building up.

Is the £100 penalty charged if I owe no tax?

Yes. The £100 late filing penalty applies to a late return even if no tax is due or you have already paid.

When do daily penalties start?

Daily penalties of £10 start on 1 May 2027 if the 2025 to 2026 return is still not filed. They run for up to 90 days, a maximum of £900.

How do I avoid the 5% late payment penalty?

Pay the tax you owe before the end of 2 March 2027. Tax still unpaid at that point gets a 5% penalty, with further 5% charges in August 2027 and February 2028.

What number do I call if I cannot pay my Self Assessment bill?

Call HMRC’s Self Assessment payment problems line on 0300 200 3820, Monday to Friday, 8am to 6pm. If you owe £30,000 or less you may be able to set up a plan online instead.

Sources

Rates, thresholds and rules in this guide were checked against HMRC and GOV.UK guidance on 6 November 2026. Tax rules change, so check the current position on GOV.UK or with a qualified adviser before acting. This guide is general information, not personal advice.