When is the self-assessment tax return deadline?

More than 12 million people must file a self-assessment tax return every year.

This includes self-employed workers, buy-to-let landlords, investors that need to pay tax on income or profits, and those paying back Child Benefit.

The deadline to submit your 2023/24 online tax return and pay your tax bill was 31 January 2025. An estimated 1.1 million taxpayers missed the deadline this year, according to HMRC.

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Not everyone is required to complete a tax return, but if HMRC was expecting one from you and you missed the deadline, you will be racking up financial penalties plus interest on any unpaid tax.

You should get your paperwork in order and file your tax return as soon as possible.

It can also be a good idea to file your tax return early, rather than waiting until shortly before the deadline. We look at when you will need to complete your tax return for the 2024/25 tax year.

When is the self-assessment tax return deadline?

There are different deadlines in place for filing your self-assessment tax return, based on how you do it.

If you submit a paper tax return, then the documentation needs to be with the taxman by midnight on 31 October.

The vast majority of people file their tax return online, and there is a later deadline of midnight on 31 January.

So, the deadline to file your 2024/25 tax return is 31 October 2025 if you submit by paper, or 31 January 2026 if you complete it online.

The January deadline is not only when you need to file your return, but also when you need to pay any outstanding income tax – regardless of whether you file a paper or online return.

If you make payments on account, you’ll also need to make your first payment by 31 January. The second payment on account is due by 31 July.

If you haven’t done a self-assessment before, the deadline to register is 5 October.

There’s one other deadline you need to know about. If you owe less than £3,000 in income tax from self-employment and are currently employed or receiving a company pension, HMRC can automatically adjust your PAYE tax code to collect the tax owed.

If you want to pay your tax bill in this way, you must submit your self-assessment return by midnight on 30 December, instead of 31 January. If you’re filing a paper tax return, the 31 October deadline still applies.

What happens if I miss the self-assessment tax return deadline?

Penalties will apply if you file your self-assessment tax return after the deadline.

One day late

There is a £100 fine for filing the return late, even if only by one day.

Three months late

After three months (so if you file an online tax return, that means from 1 May), you get hit with additional daily penalties of £10, up to a maximum of £900.

Six months late

After six months, a further penalty applies – either 5% of the tax due or £300, whichever is greater.

12 months late

The same fine (5% or £300) applies again once you are 12 months late.

There are also penalties for paying your tax bill late, even if you filed on time. These include 5% of the unpaid tax at 30 days, six months and 12 months. Interest is also charged at base rate plus 4%, meaning it’s currently an eyewatering 8%.

“Although the deadline was back in January, it's likely that hundreds of thousands of people still haven't filed their tax returns,” said Alastair Douglas, chief executive at financial services company TotallyMoney.

Douglas explains that any penalties need to be paid within 30 days of receiving a penalty notice. You can pay in several ways, including through bank transfer, using your debit or credit card, or by sending a cheque.

If you have a reasonable excuse for why your tax return is late, you can challenge your penalty. This could include a death or serious illness in the family, or difficulties with HMRC’s online service.

Some people also put off dealing with their paperwork because they can’t afford to pay their tax bill – but this is a bad idea.

“If you’re struggling to pay your bill in full, then head over to the HMRC website where you might be able to set up a payment plan under a ‘Time to Pay’ arrangement,” Douglas said.

What happens if I make a mistake with my tax return?

If you make a mistake with your tax return, you can correct it even after the deadline. Tax return mistakes can be corrected within 12 months of the tax return being filed, with a new tax bill due on the updated return.

You will need to wait at least 72 hours after filing your return to make any changes.

How do payments on account work?

Payments on account are advance payments you make towards your next tax bill, ahead of the 31 January deadline.

There are two payments on account due, each of which is around half of the previous year’s tax bill. Once you file your tax return, you can then determine whether a top-up payment is needed in order to clear the amount owed, or whether you can claim a refund.

The first payment on account must be paid by 31 January, while the second must be paid by 31 July.

So for example, if your tax bill for 2023/24 was £20,000, you will be required to make two payments on account, worth £10,000 each, for the 2024/25 tax year, with those payments required by 31 January and 31 July 2025.

If you believe your tax bill is likely to be lower than the previous tax year, you can apply to have your payments on account reduced.

How to hit the tax return deadline on time and avoid overpaying

There are certain things to bear in mind if you want to remove the stress involved with filing a self-assessment tax return correctly and on time.

First and foremost, it’s a really good idea to give yourself as much time as possible.

Registering to file a tax return can take a while, since you’re relying on the postal service to send you a Unique Taxpayer Reference (UTR) number. The earlier you start this process, the better. Remember, the deadline to register for self-assessment is 5 October.

Similarly it’s crucial you take the time to gather together all the relevant paperwork before you start attempting to fill in the return. That means bringing together your payslips, details of other income sources, savings and investments, pension contributions and charitable donations.

Understanding the tax allowances and tax reliefs that apply to you means you may be able to reduce the actual tax you have to pay.

This can include the working from home allowance, the uniform allowance and the trading allowance of up to £1,000 for casual income.

Once you’ve got that information together, it’s important to double-check the calculations and make sure everything is accurate before you submit. Even if you make errors in good faith, you may be charged penalties by HMRC.

When the submission is finished, it’s useful to take lessons from it to work out how to reduce your tax bill in future years. In particular, topping up your pension can lower your tax liability, as well as help provide for your retirement.

You should also keep an eye on any changes to your tax code and check that it remains accurate for your circumstances.

Who needs to file a self-assessment tax return?

If your only source of income is your salary and you are not self-employed, then you probably don’t need to file a tax return. Your income tax will be deducted from your salary before you receive it through PAYE (which stands for “pay as you earn”).

Pension income is generally taxed through PAYE too, if you exceed the personal allowance.

However, if you also earn income from savings and investments held outside an ISA, a business, a second home, or another source, then it is likely you will need to file a tax return. The same is true if you are self-employed.

In recent years, more people have found themselves being dragged into the self-assessment net thanks to the effects of fiscal drag. This is because inflation has been high, but tax thresholds have remained frozen. As a result, the tax-free allowances are worth less than they once were in real terms.

Some allowances have even been cut, including the dividend and capital gains tax allowances. This means investors can wrack up less in tax-free income and gains before a tax bill is due.

If you’re unsure whether you need to file a tax return, HMRC’s online tool helps you check.