Self Assessment deadlines: when to register, file and pay

This article was written by FreeAgent’s Content team and our Chief Accountant, Emily Coltman FCA.

The deadline for filing your Self Assessment tax return is 31st January, but there are a number of other deadlines relating to Self Assessment that pop up throughout the year. To help you avoid any nasty surprises, we’ve put together a guide to the most important dates.

Let’s look at each of the above dates in a bit more detail:

5th October: registering for Self Assessment

If you receive income above the trading allowance, and that income isn’t taxed at source (for example, by your employer through PAYE), you’ll have to register for Self Assessment, which lets HMRC know that they can expect a tax return from you.

The deadline for registering is 5th October in your business’s second tax year. For example, if you need to pay tax on income for the tax year that runs from 6th April 2023 to 5th April 2024, you must register for Self Assessment by 5th October 2024. You can still register after the deadline, but you could be fined.

If you registered and filed a tax return last year, you don’t need to register again. However, if you filed a tax return last year but aren’t planning on filing one this year, you need to let HMRC know.

Midnight on 31st October: filing a paper tax return

HMRC encourages taxpayers to file Self Assessment online, which you can do through the HMRC website or using software such as FreeAgent, but you might still need to file a paper tax return in certain cases. Paper returns must be filed by midnight on 31st October following the end of the relevant tax year.

Bear in mind that this is the date by which HMRC needs to have received the return, so make sure you allow plenty of time to print the forms, fill them in and post them to HMRC.

Midnight on 30th December: letting HMRC know to collect Self Assessment payments through PAYE

If you owe less than £3,000 in Income Tax from self-employment and are currently employed or receiving a company pension, HMRC will automatically adjust your PAYE tax code in order to collect the tax that you owe. This will be deducted from your salary or pension payments in equal instalments over 12 months.

If you would like to pay your tax bill in this way, you must submit your Self Assessment tax return by midnight on 30th December following the end of the relevant tax year. If you submit your return online before the deadline, this method of payment will be set up automatically. If you’re filing a paper tax return, the 31st October filing deadline still applies.

If you would prefer to pay this tax directly to HMRC, you can opt out of paying it through PAYE. If you’re filing your return through FreeAgent, you’ll see this option under ‘Tax Refund and Payments’ on the Main Return.

Midnight on 31st January: filing your return online

This is the deadline that keeps a lot of small business owners and their accountants or bookkeepers up late on the last day of January. If you use FreeAgent, your Self Assessment tax return is auto-populated from the information you enter throughout the year. If you're a sole trader, parts of the Self Employment form are filled in for you.

Filing your return through FreeAgent is usually a case of checking over the numbers, filling in a few extra details and clicking a button to file to HMRC directly from the software.

Midnight on 31st January: paying your bill

Don’t forget that as well as filing your return, you also have to pay it by the same deadline. This means that it’s a good idea to complete your tax return as soon as you can in order to allow yourself plenty of time to pay. You can find out more about how to pay your bill on HMRC’s website.

Midnight on 31st January: first payment on account

This deadline catches a lot of small businesses out in their first year of Self Assessment. Not only do you need to pay the tax bill for the first year, but if your bill for Income Tax (and Class 4 National Insurance if you're self-employed) was more than £1,000 and you’ve paid less than 80% of the tax you owe at source, you also have to make an advance payment towards next year’s Self Assessment bill.

This is known as a payment on account and is equal to half of the previous year’s tax bill. You will have to make a payment on account on this date every year. However, in your business's first year you will have to pay half of next year’s Self Assessment bill at the same time as the full bill for the first year.

Midnight on 31st July: second payment on account

For those businesses that are required to make payments on account, the second payment is due on 31st July. Like the first payment, this is equal to half of your previous year’s tax bill. So in theory, if your earnings are the same as the previous year you will have paid your Self Assessment bill in full by this point.

When you file your next tax return, if it transpires that your two payments on account amount to more than you actually owed then you’ll receive a tax rebate, but if they were less, you will have to make a balancing payment (by the 31st January deadline) in order to make up the difference.

Stay ahead of the Self Assessment deadlines with FreeAgent’s Tax Timeline

FreeAgent’s unique Tax Timeline feature shows you a clear overview of your tax position so you can see all your liabilities build up over time and know exactly what you owe and when it’s due.

With your bank account linked to your FreeAgent account, you can get an up-to-date and accurate picture of how much money you have in your account.

Find out more about Self Assessment in FreeAgent.