When is the Self Assessment deadline?

For the 2025/26 tax year, the usual online return deadline is 31 January 2027. The paper deadline is 31 October 2026. The balancing payment and any first payment on account are normally due on 31 January 2027 too. A notice issued late can set a different filing deadline.

What happens if I miss the Self Assessment deadline?

File as soon as possible and pay what you can. Late filing penalties can apply even if no tax is due, and unpaid tax can attract interest and late payment penalties. Contact HMRC about a payment plan if needed. You can appeal a penalty if you have a reasonable excuse.

What is the fine for a late tax return?

Under the standard regime for returns outside MTD for Income Tax, the initial penalty is £100 even if no tax is due. After 3 months, daily penalties of £10 can apply for up to 90 days. After 6 months and again after 12 months, a further penalty is 5% of the tax due or £300, whichever is higher. More serious failures can lead to higher penalties. HMRC is introducing a points-based system for people within MTD.

When is the deadline to register for Self Assessment?

If this is your first return for the 2025/26 tax year, the registration deadline is 5 October 2026. If you have missed it, register as soon as possible and check your filing and payment responsibilities with HMRC.

What time on 31 January is the deadline?

Midnight, at the end of 31 January. For the 2025/26 online return, that is the end of 31 January 2027. Allow time to submit and check that HMRC has received the return rather than leaving it to the last moment.

Can I get an extension?

Generally, no. If HMRC issues a notice to file late, you normally get 3 months from the date of the notice to send the return. That does not automatically extend the tax payment deadline. Reasonable excuse appeals can apply to penalties, but are not a general extension of the deadline.

Guides

Last updated 14 October 2026

Self Assessment deadlines

This guide covers the 2025/26 tax year, from 6 April 2025 to 5 April 2026, with online returns due on 31 January 2027. We update it every year.

Key dates for the 2025/26 tax year

5 October 2026
Register for Self Assessment if this is your first return. If you have missed this date, register as soon as possible.
31 October 2026
Deadline for HMRC to receive a paper tax return.
30 December 2026
Online deadline if you are employed and want HMRC to collect what you owe, under £3,000, through your tax code. HMRC's other eligibility conditions also apply.
31 January 2027
Online return deadline, balancing payment for 2025/26 and the first payment on account for 2026/27, if payments on account apply.
31 July 2027
Second payment on account for 2026/27, if payments on account apply.

Late filing penalties

These are the standard late filing penalties for returns that are not within Making Tax Digital for Income Tax. HMRC is introducing a points-based system for people within MTD, so check which regime applies to you.

An initial £100 penalty, even if no tax is due
After 3 months, £10 a day for up to 90 days
After 6 months, a further penalty of 5% of the tax due or £300, whichever is higher
After 12 months, another penalty of 5% of the tax due or £300, whichever is higher; more serious failures can lead to higher penalties

Read our MTD for Income Tax guide

Late payment

Interest is charged from the day after the payment deadline. Late payment penalties can also apply. Filing your return and paying the tax are separate responsibilities, so sending the return does not stop interest on an unpaid balance.

If you have missed a deadline

File the return as soon as possible and pay what you can. If you cannot pay in full, contact HMRC about a payment plan. Do not wait for the payment position to be resolved before filing.

You may be able to appeal a penalty if you have a reasonable excuse. HMRC considers the circumstances and the evidence, so an appeal is not an automatic cancellation.

Payments on account, simply explained

Payments on account are advance payments towards your next Self Assessment bill. If they apply, you normally make two instalments, based on the previous year's bill, in January and July. Once the actual bill is known, a balancing payment settles any difference.

If you expect your bill to be lower, you may be able to reduce the payments on account. Reducing them too far can lead to interest, so check the figures before asking HMRC to change them.

Amending a return

You can normally amend a return within 12 months of the filing deadline. For a 2025/26 return with the usual online deadline, that normally means by 31 January 2028. After that, the process depends on what needs correcting. Speak to us rather than assuming it is too late.

MTD quarterly updates

People within MTD for Income Tax have digital record-keeping and quarterly update responsibilities as well as their year-end reporting. An annual filing date does not replace those quarterly deadlines. Check our MTD guide to understand the process and whether it applies to you.

Making Tax Digital for Income Tax

Need a hand with your return or an overdue deadline? Book a free proposal meeting.

Written by Bee Motion

Bee Motion Accounting Limited

This guide is general information, not advice for your individual circumstances. It reflects the rules at the last-updated date. Speak to us if you need help checking your position.