Self assessment deadlines

If you pay tax using self assessment, it's essential that you know the deadlines. If you miss the deadlines for registering, filing your tax return and paying the tax you owe, you can face severe penalties

Self assessment registration deadline

If you need to complete a self assessment return, it is your responsibility to register with HMRC. Self assessment typically applies if you are self-employed, have a high income or have complicated tax affairs. You can use an online tool to check whether you need to register.

You must register by 5 October after the end of the tax year. For example, if you need to complete a tax return for the tax year 6 April 2023 – 5 April 2024, you must register by 5 October 2024.

If you completed a self assessment return last year, there is no need to register again this year. HMRC should automatically remind you of the need to complete a return (but it is your responsibility whether they remind you or not).

Tax return deadlines

The deadline for filing your self assessment return depends on whether you file online or by post.

If you want to complete a paper tax return, the deadline is 31 October after the end of the tax year. That is the date by which HMRC must receive the return, so allow a few days for postal delays (and consider sending the return using guaranteed or tracked post).

If you file online, the deadline is 31 January. This is also the deadline by which you must pay any tax you owe (see below). So you may want to file your tax return earlier to make sure there is time to work out and pay the bill.

There is an earlier online filing deadline if you want to ask HMRC to collect any tax you owe through PAYE. This is usually possible if you already pay tax through PAYE and owe less than £3,000 – but you must file online by 30 December (or on paper by 31 October).

Tax payment deadlines

The deadline for paying all the tax you owe is 31 January after the end of the tax year.

However, you normally also have to make two ‘payments on account' towards the following tax year. The first payment on account is also due by 31 January, followed by a second payment on account due by 31 July (six months later).

• Payments on account are estimated amounts, based on your previous tax return. Each payment on account is half the previous year's tax bill.
• You don't have to make payments on account if your tax bill is less than £1,000 or you have already paid at least 80% of the tax you owe.
• You don't have to make payments on account for any capital gains tax included in your bill.

If your actual tax bill the following year turns out to be higher than the payments on account you have made, you make a final ‘balancing payment' by 31 January. You can find an example of how payments on account work from GOV.UK.

If you are completing your first self assessment tax return, the payment due by 31 January may be higher than you expect:

• You have to pay your entire self assessment tax bill (as you have not made any payments on account previously).
• You may also have to make a first payment on account, adding an extra 50% to the amount due.

The payment deadlines are the dates by which HMRC must receive the payment. Allow for payment delays, depending on how you pay your bill. For example, setting up a new direct debit might take up to a week.

If you cannot afford to pay your tax bill on time, you should contact HMRC's Business Payment Support Service (0300 200 3835) straight away. It may be possible to agree an instalment plan.

Self assessment penalties

There are substantial penalties for missing the deadlines for filing your tax return and paying any tax due.

If you miss the 31 January filing deadline, you face fines of:

• an initial £100;
• after three months, a further £10 a day up to a maximum of £900;
• after six months, a further £300 or 5% of the tax owing, whichever is greater;
• after 12 months, another £300 or 5% of the tax owing.

Fines can be even higher if HMRC suspects that you are deliberately concealing information.

If you fail to pay the tax due on time, you can be charged interest plus further fines of:

• 5% of tax still outstanding more than 30 days after due date;
• another 5% after six months;
• another 5% after twelve months.

There can also be penalties if you fail to register for self assessment at all, either deliberately or because you do not realise that you need to. Penalties can be up to 100% of the tax owed, but HMRC will usually not penalise you if you miss the registration deadline (5 October) but end up paying the tax on time (by 31 January).

If you miss a deadline, it's vital to contact HMRC as soon as possible. HMRC can cancel late-filing penalties if they agree that you have a reasonable excuse. Late payment penalties can be suspended in you have reached an agreement with HMRC to pay in instalments.