When is the Self Assessment tax return deadline?

The deadline for filing a Self Assessment tax return depends on the tax year and how you submit your return. For the 2024-25 tax year, which ended on 5 April 2025, the deadline for filing the online Self Assessment tax return is midnight on 31 January 2026.

There are several other important dates that taxpayers need to keep in mind to avoid unnecessary penalties. Anyone who is self-employed or earning untaxed income, such as rental income, usually needs to file a tax return by 31 January each year. Missing the deadline can lead to fines, and these penalties increase the longer the return is delayed. This is why it is always better to prepare your tax return well in advance rather than waiting until the last minute.

The previous tax year ran from 6 April 2024 to 5 April 2025. Any untaxed income earned during this period must be declared, and the Self Assessment tax return must be submitted by 31 January 2026. Many taxpayers are caught out because the next deadline arrives sooner than expected, so keeping track of the dates can help avoid stress and last-minute issues.

Key Takeaways

• The online Self Assessment tax return deadline for the 2024–25 tax year is 31 January 2026, with paper returns due by 31 October 2025.
• Missing the deadline leads to an automatic £100 penalty, even if no tax is owed.
• Newly self-employed individuals must register for Self Assessment by 5 October 2025.
• Income earned after 6 April 2025 falls into the 2025–26 tax year, with a filing deadline of 31 January 2027.

Important Self Assessment dates to remember

5 October 2025

This is the deadline for newly self-employed individuals to register for Self Assessment with HMRC. If you are already registered, you do not need to register again.

31 October 2025

This is the deadline for submitting a paper Self Assessment tax return for the 2024–25 tax year. Most people now file online, as it is quicker and more convenient. With HMRC continuing to move towards digital reporting, paper returns are becoming less common.

30 December 2025

This is the deadline for submitting your tax return online if you want the tax you owe to be collected through your PAYE tax code. This option is only available if:

• You are employed or receive PAYE income
• Your Self Assessment tax bill is £3,000 or less
• The tax has not already been paid

31 January 2026

This is the main Self Assessment deadline. By this date, you must:

• Submit your online tax return
• Pay any tax owed
• Make the first payment on account, if applicable

Missing this deadline results in an automatic £100 penalty, even if you do not owe any tax.

31 July 2026

This is the deadline for making the second payment on account, where required. Payments on account usually apply if your previous year’s tax bill was more than £1,000.

If you continue earning untaxed income after 6 April 2025, it will fall into the 2025–26 tax year, which ends on 5 April 2026. The deadline for filing the Self Assessment tax return for that year will be 31 January 2027.

Making Tax Digital and future changes

From April 2026, Making Tax Digital for Income Tax will apply to self-employed individuals and landlords with income over £50,000. This will require keeping digital records and submitting regular updates to HMRC using compatible software. Although annual tax returns will still be required, taxpayers should start preparing early for these changes.

Taxpayers should start thinking about their tax return as soon as they begin earning income. Keeping business and personal finances separate, saving receipts for allowable expenses, and tracking income regularly can make the process much easier. Many people now use simple accounting software or online spreadsheets to stay organised throughout the year.

Frequently Asked Questions

When is the online Self Assessment tax return deadline for 2026?

The online Self Assessment tax return deadline for the 2024–25 tax year is 31 January 2026.

What happens if I miss the Self Assessment deadline?

If you miss the deadline, HMRC charges an automatic £100 penalty, even if no tax is owed. Additional penalties and interest apply the longer the return remains unfiled or unpaid.

Can I still file a paper tax return?

Yes, but the paper tax return deadline is earlier. For the 2024–25 tax year, paper returns must be submitted by 31 October 2025.

When do I need to register for Self Assessment?

If you are newly self-employed or start earning untaxed income, you must register for Self Assessment by 5 October following the end of the tax year.

What are payments on account?

Payments on account are advance payments towards your next tax bill. They usually apply if your previous year’s tax bill was more than £1,000 and are due on 31 January and 31 July.

What is the deadline for the next tax year?

For income earned during the 2025–26 tax year, the Self Assessment deadline will be 31 January 2027.