What Are the Deadlines for Self-Assessment Tax Returns?
If you’re self-employed or have income that isn’t automatically taxed through PAYE, you may need to submit a Self-Assessment tax return. Getting the dates right for submitting your tax return is crucial to avoid penalties. In this blog, we’ll explain the key deadlines you need to know to stay on track with your Self-Assessment.
Table of Contents
Self Assessment Tax Return Deadlines
1. Deadline for Registering for Self-Assessment: 5 October
If you need to register for Self-Assessment for the first time, you must do so by 5 October in your second tax year. For example, if you became self-employed in the 2025/26 tax year but missed the initial deadline, you must register by 5 October 2026. This registration gets you a Unique Taxpayer Reference (UTR) number, which you’ll need before you can submit any tax returns. Missing this deadline can result in penalties and complications with your tax filing.
2. Paper Tax Returns: 31 October
If you are submitting your tax return on paper, you need to make sure it’s filed by 31 October after the end of the tax year. For example, if you’re filing for the 2025/26 tax year (which ended on 5 April 2026), the deadline to submit a paper return is 31 October 2026.
This deadline is strict. If you miss it, you may face penalties or be required to file your tax return online instead, which will give you a little more time.
3. Online Tax Returns: 31 January
For those who prefer to submit their tax returns online, the deadline is much later: 31 January. This date is the deadline for submitting your online tax return for the previous tax year, and also the deadline for paying any tax you owe. For the 2024/25 tax year, the deadline for online filing and payment is 31 January 2026.
This online deadline is very important, as failing to submit on time will result in a £100 fine, even if you don’t owe any tax. If you continue to delay, the fine increases and additional charges are added.
4. Paying Your Tax: 31 January
Along with submitting your Self-Assessment online by 31 January, you also need to pay any tax owed by the same date. If your tax return shows that you owe money, it must be paid by 31 January. If you miss this payment, you will be charged interest on the unpaid tax, and penalties can be added.
5. Second Payment on Account: 31 July
Self-employed individuals may need to make payments on account. This is a way of paying your tax in advance for the following year. Payments on account are usually due on 31 January and 31 July. If you are required to make these payments, you need to pay half of your estimated tax bill for the next year by 31 July.
For example, if you filed your 2024/25 tax return by 31 January 2026 and it shows you owe £2,000, you would need to pay £1,000 by 31 July 2026 as part of the payment on account.
6. Deadline for Making Changes to Your Tax Return: 31 January (One Year After Filing)
If you realise after submitting your Self-Assessment that you made a mistake or forgot to include something, you can make changes. However, you need to do this by 31 January of the year after you submit your tax return. For example, if you submitted your tax return for 2024/25 by 31 January 2026 and later discovered an error, you must make any changes by 31 January 2027.
This is important because if you leave it too late, HMRC may not accept the changes or offer a refund for any overpaid tax.
Read: Benefits of Filing Self Assessment Tax Return Early
What Happens If You Miss the Tax Return Deadlines?
Missing any of the self-assessment deadlines can result in fines and interest. Even if you’re only a few days late, HMRC will charge you £100 for missing the filing deadline. After that, additional penalties can be applied.
If you file your return or make payment late, you could face:
- A £100 fine for missing the 31 January deadline (even if you don’t owe any tax).
- Additional fines if you continue to be late, increasing the longer the delay goes on.
- Interest on overdue tax.
- Penalties for non-payment.
Therefore, it’s crucial to keep track of these deadlines and submit your tax return and payment on time to avoid any additional charges.
Can You Get an Extension on a Self-Assessment Tax Return?
HMRC typically won’t grant extensions for self-assessment returns. The filing deadlines are firm: 31 October for paper submissions and 31 January for online ones.
That said, if circumstances genuinely prevented you from meeting the deadline, you can contest any penalties. Valid reasons might include serious illness, a death in the family, problems with HMRC’s website, or unforeseen events beyond your control.
If this applies to you, file your return straight away and get in touch with HMRC to explain what happened. They’ll assess whether your reason is legitimate and may waive or reduce the penalty accordingly.
In rare situations, such as technical glitches or genuine personal hardship, you may be able to request extra time through your HMRC account or by ringing the Self-Assessment helpline. But don’t count on it. Your safest bet is to submit well before the deadline.
How do I avoid late self-assessment penalties?
To avoid any issues with meeting your Self-Assessment deadlines, here are some helpful tips:
- Set reminders: Use your phone or calendar to set reminders for filing and paying your tax.
- Start early: Don’t wait until the last minute to fill out your tax return. The earlier you start, the easier it will be.
- Consider using accounting software: This can help you track your income and expenses, making it easier to fill out your tax return when the time comes.
- Get help if needed: If you’re unsure about anything, don’t hesitate to ask an accountant or tax professional. They can guide you through the process and help you meet deadlines.
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Conclusion
The deadlines for self-assessment tax returns are important to remember, and they differ depending on whether you’re filing on paper or online. The key deadlines you need to be aware of are:
- Paper Tax Returns: 31 October
- Online Tax Returns: 31 January
- Paying Your Tax: 31 January
- Second Payment on Account: 31 July
- Deadline for Making Changes: 31 January (one year after filing)
To avoid penalties and interest, ensure that you submit your tax return and payment on time. Planning ahead and staying organised will help you meet these deadlines without stress.
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