UK tax deadlines: at a glance
- What do I need to know? The UK tax deadline is 31 January for online Self-Assessment
- What does it mean for me? Completing your tax return in advance means you can plan ahead and avoid expensive fines.
- Why does it matter? Once you know how much tax you owe, you could set aside your money in a high-interest savings account until you pay your bill.
The guide to tax deadlines in the UK
Filing your tax return ahead of the deadline helps you plan for your bill. You can then pay it early to avoid potential fines and administrative headaches or set your tax money aside until it’s due. That way, you can continue to grow your cash until you settle your bill.
In this guide, we explain everything you need to know about the UK tax deadline. You’ll learn about tax returns, why they matter, and when you need to file one with HMRC.
What is a tax return?
A document that you submit, either in paper format or online, to HMRC detailing your accounts and explaining how much tax you owe. Think of them like an annual audit of your finances. In the UK, the process of submitting a tax return is known as your ‘Self-Assessment’.
If you’re self-employed or earn income from property, savings, or investments, you may need to file a Self-Assessment tax return. You’ll also need to file a tax return if you earn an income over £150,000 a year.
The tax deadline is the last day you can submit this information without paying a fine.
Tax rules can be confusing and subject to change. If you’re unsure whether you need to submit a tax return or not, consult a qualified financial adviser.
Why do you need to know your tax deadline?
Understanding tax deadlines means you can prepare everything in advance and file your tax return early. This allows you to:
- Maximise interest and tax relief: The earlier you file your taxes, the sooner you receive your bill. This means you have time to do more with your money before the payment deadline - like placing it in high-interest accounts. You could also think about increasing your pension contributions.
- Access wealth: You’ll have to provide your tax returns if you apply for a mortgage, loan, or other investment. Paying on time shows you’re responsible with money and means you’re more likely to get approval for future lines of credit.
- Avoid fines and penalties: HMRC charges you penalty fees for missing your tax return deadline. Up to three months late, you’ll be fined £100, with the fine increasing the later you submit your taxes. HMRC will also charge you interest the longer you take to pay.
- Relieve admin headaches: You could be asked for more financial information, more frequently if you miss the deadline - time that could be better spent exploring savings or investment strategies.
When does the 2025/26 tax season start?
The UK tax year runs from 06 April until midnight the following 05 April. The 2025/26 tax year starts from 06 April 2025.
When are taxes due?
While the tax year ends on 05 April, your return isn’t due on this date. This is because HMRC needs time to verify the accuracy of your accounts before the end of the tax year. There are three important dates to know relating to your tax deadlines:
- 31 October: The deadline for submitting a paper tax return. If you miss this deadline, you can’t register online instead.
- 31 January: The deadline for submitting your tax return online.
- 31 July: This deadline is known as the ‘second payment on account’ and is offered to high earners to help them spread significant tax contributions over two payments.
These are the last dates you can file your tax return without being fined.
But it’s possible to file your tax return early to get your bill, which you can pay later.
When does my tax return need to be done?
You can start filling in your tax return as soon as the online service is available. This is usually in April of the current tax year.
Getting your Self-Assessment ready before the tax deadline can help you understand your tax bill and avoid fines. But the hard deadline is 11.59 pm on 31 January.
When is the deadline to register for Self-Assessment?
If you’ve not submitted a tax return before, you’ll need to apply for a Self-Assessment.
The deadline to register for Self-Assessment is 05 October.
What tax year is due now?
Your next tax deadline is always for the previous tax year. So, the next tax deadline on 31 January 2026 would be for the 2024/25 tax year.
Frequently asked questions about the UK tax deadline
How much does HMRC charge for a late tax return?
Fines for a late tax return will depend on how long after the deadline you submitted it. If your tax return is up to three months late, HMRC charge £100. This then increases the later you submit. HMRC charge interest on these fines.
Do I have to pay my tax bill by 31 January? Staying ahead of the UK tax deadline
Filing your tax return ahead of the deadline gives you time to understand your tax bill. It can also help to prove you’re responsible to lenders and mortgage providers.
This gives you more options when it comes to growing your wealth.
Earn more on the money you keep with Flagstone
Once you’ve submitted your taxes, you know exactly where your money’s going. So, you can start to plan for what’s yours to keep, and what you’ll need to pay as tax.
And until the tax deadline, you can continue to invest the money you’ll need to pay as tax. This is where low-risk, high-interest accounts come in.
Flagstone offers access to accounts from 60+ banks, all in one place, with one login.
