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Missing a tax deadline can turn a straightforward Self Assessment into an expensive and stressful problem. Whether you are self-employed, a landlord, a freelancer or have other untaxed income, knowing the Self Assessment Tax Deadline is essential for avoiding penalties and keeping your tax affairs in order.
For the 2025/26 tax year, which runs from 6 April 2025 to 5 April 2026, most taxpayers filing online must submit their return and pay any tax owed by 11:59 pm on 31 January 2027. If you file a paper return, the deadline is 31 October 2026.
Understanding the different dates can help you plan ahead, gather your records and avoid leaving everything until the last minute.
The Self Assessment Tax Deadline is the date by which HM Revenue and Customs (HMRC) must receive your tax return and, where applicable, your tax payment.
|
Deadline |
What it means |
|
5 October 2026 |
Generally the registration deadline for those who need to register for Self Assessment for 2025/26 |
|
31 October 2026 |
Paper tax return deadline |
|
30 December 2026 |
Deadline for some taxpayers who want tax collected through PAYE |
|
31 January 2027 |
Online tax return and main tax payment deadline |
|
31 July 2027 |
Second payment on account, where applicable |
These dates are based on HMRC's current guidance for the 2025/26 tax year.
The self assessment tax return deadline applies to most taxpayers who need to complete a return. Filing online gives you considerably more time than submitting a paper return, but it is still sensible to prepare your information well before January.
If you need to complete a Self Assessment tax return for the 2025/26 tax year and have not previously filed one, you generally need to tell HMRC by 5 October 2026.
This date is particularly important for people who have started receiving income that is not taxed automatically, such as income from self-employment, property or certain investments. You may also need to register if you previously registered for Self Assessment but did not need to submit a return for 2024/25.
The self assessment tax return deadline should not be confused with the registration deadline. Registering tells HMRC that you need to complete a return; it does not mean that your tax return itself must be submitted by 5 October.
If you register after 5 October 2026, HMRC may issue a different filing deadline, generally giving you three months from the date of its notice. However, the tax you owe will still normally need to be paid by 31 January 2027.
If you choose or need to file a paper Self Assessment tax return, HMRC must receive it by 11:59pm on 31 October 2026.
The self assessment tax form deadline is earlier than the online filing deadline, giving taxpayers who file electronically an additional three months.
For the 2025/26 tax year, the SA100 paper tax return can be submitted from 6 April 2026. HMRC must receive the completed form by the October deadline to avoid a late filing penalty.
If you are filing by post, do not leave it until the final few days. Postal delays could cause your return to arrive after the deadline. Online filing is generally more convenient and gives you more time to prepare your return.
There are some exceptions and special circumstances where different filing dates can apply, so check your HMRC notice if it gives you a specific deadline.
The 30 December 2026 deadline applies to some taxpayers who want HMRC to collect their Self Assessment tax through their PAYE tax code.
This option can allow eligible taxpayers to have the amount owed deducted from their salary or pension rather than paying the full amount separately by 31 January. However, you must submit your online tax return by 30 December for HMRC to consider collecting the tax through PAYE.
Not everyone can use this option. Your circumstances, the amount you owe and the way you are taxed can affect whether PAYE collection is available.
Therefore, if you are considering this method, check your eligibility carefully and do not assume that submitting after 30 December will still allow the tax to be collected through your tax code.
For most taxpayers, 31 January 2027 is the most important date in the uk self-assessment tax return deadline calendar.
By 11:59pm on this date, you normally need to:
HMRC confirms that online returns must normally be submitted by 31 January following the end of the relevant tax year. Your Self Assessment tax bill is also generally due on the same date.
This is why leaving your return until January can be risky. You need enough time to gather income records, business expenses, bank statements, pension information and other relevant documents, calculate your liability and arrange payment.
Submitting your return early can make budgeting easier because you will know how much tax you are expected to pay before the deadline.
31 July 2027 is the deadline for making payments on account.
Payments on account are advance payments towards your next Self Assessment tax bill. They are normally split into two installments, with one due on 31 January and the second due on 31 July. Each installment is usually half of the previous year's tax bill, although your circumstances can affect the calculation.
You may not have to make payments on account if, for example, your previous year's tax bill was less than £1,000 or more than 80% of your tax was already collected outside Self Assessment.
Your HMRC account or Self Assessment statement should show whether payments on account apply to you and how much you need to pay.
Missing the Self Assessment Tax Deadline can lead to significant penalties, so it is important to file your tax return as soon as possible if you have missed the deadline. HMRC may apply:
|
Missing Duration |
Penalty |
|
Immediately |
Initial £100 penalty |
|
After 3 months |
£10 per day, up to a maximum of £900 |
|
After 6 months |
5% of tax due or £300, whichever is greater |
|
After 12 months |
Further 5% of tax due or £300, whichever is greater |
|
Late payment |
Interest and late payment penalties may also apply |
Interest and late payment penalties may also apply if you do not pay the tax you owe on time. If you have missed the self assessment tax return deadline, do not delay further. Submit your return and pay any outstanding tax as soon as possible to minimise further charges.
Waiting until January can make your tax return unnecessarily stressful. Instead, prepare throughout the year.
Keep records of:
Reviewing these records early gives you time to identify missing information and correct mistakes before submitting your return.
It is also worth checking the self assessment tax form deadline well in advance if you intend to file on paper.
Knowing the Self Assessment Tax Deadline is one of the simplest ways to avoid unnecessary tax penalties and last-minute pressure. For most taxpayers completing an online return for 2025/26, 31 January 2027 is the key date to remember.
At PHS Associates, we provide professional Self Assessment support to help individuals and self-employed professionals manage their UK tax responsibilities. From reviewing your income and allowable expenses to preparing and submitting your tax return, our team can help you stay organised and meet the relevant HMRC deadlines.
Need help with your Self Assessment tax return? Book a free consultation today for professional guidance and make your tax filing simpler and stress-free.
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