Who Needs to Complete a Self Assessment Tax Return?

Not everyone needs to complete a Self Assessment tax return. If your tax is deducted automatically through PAYE (Pay As You Earn), you may not need to do anything else. However, if you're self-employed, receive rental income, or have other sources of untaxed income, you'll need to register for Self Assessment and submit a tax return each year.

What is Self Assessment?

Self Assessment is the system HMRC uses to collect Income Tax from people and businesses with income that hasn't already been taxed. Most employees and pensioners have their tax deducted automatically, but if you have other income, you'll need to report it through a Self Assessment tax return.

The tax return covers income you receive during the tax year, which runs from 6 April to 5 April. For example, the 2025/26 tax year runs from 6 April 2025 to 5 April 2026.

Who must send a tax return

You must send a tax return if any of the following applied to you in the last tax year:

Self-employed and business income

• You were self-employed as a sole trader and earned more than £1,000 (before deducting any expenses you can claim tax relief on)
• You were a partner in a business partnership

Property income

• You earned money from renting out a property, including holiday lets

Capital gains

• You had to pay Capital Gains Tax when you sold or disposed of something that increased in value (such as shares or a second home)

High earners with children

• You had to pay the High Income Child Benefit Charge and do not pay it through PAYE

Off-payroll workers

• You are an off-payroll worker repaying a student or postgraduate loan

When you may need to send a tax return

You may also need to send a tax return if you have any untaxed income, such as:

• Tips and commission
• Income from savings, investments and dividends
• Foreign income

You must also send a return if HMRC specifically asks you to do so.

Additional income you need to tell HMRC about

Some types of additional income may require you to complete a Self Assessment tax return. This includes money you earn from:

• Selling things at car boot sales, auctions, or online
• Doing casual jobs such as gardening, food delivery or babysitting
• Charging other people for using your equipment or tools
• Renting out property or part of your home, including for holidays (for example, through an agency or online platform)
• Creating content online, for example on social media

If you're unsure whether your additional income means you need to register for Self Assessment, HMRC provides an online checking service to help you work this out.

When you don't need to send a return

If all your income is taxed through PAYE and you have no other untaxed income above the thresholds mentioned above, you probably don't need to complete a Self Assessment tax return.

Optional reasons for sending a return

Even if you don't have to send a tax return, you can choose to fill one in to:

• Claim some Income Tax reliefs
• Prove you're self-employed (for example, to claim Tax-Free Childcare or Maternity Allowance)
• Pay voluntary National Insurance contributions

Important deadlines

If you need to complete a tax return and have either not sent one before, or registered previously but didn't need to send a tax return for the 2023 to 2024 tax year, you must tell HMRC by 5 October for the previous tax year.

You tell HMRC by registering for Self Assessment. You could be fined if you don't register by 5 October.

Once registered, you must:

• Submit your tax return by the deadline (31 January for online returns)
• Pay any tax owed by 31 January

How to check if you need to send a return

If you're still not sure whether you need to complete a Self Assessment tax return, HMRC provides an online checking service. This will help you work out whether your circumstances mean you need to register.

It's important to check your situation each year, as your circumstances may change. For example, if you start doing freelance work alongside your employment, or begin renting out a property, you'll need to register for Self Assessment.

What happens if you need to register

Once you've established that you need to complete a Self Assessment tax return, you must register with HMRC. They'll send you a Unique Taxpayer Reference (UTR) number, which you'll need to file your return.

After registering, you'll need to keep records such as bank statements and receipts so you can fill in your tax return correctly. You can submit your return any time after 5 April, and doing it earlier means you'll know what you owe and have time to budget for the payment.

HMRC will calculate what you owe based on what you report in your return. You can set up monthly or weekly payments to help spread the cost throughout the year if that makes it easier to manage.

Sources

• Self Assessment tax returns
• Check if you need to tell HMRC about additional income

This article provides general guidance based on current HMRC rules. For advice specific to your situation, speak to your accountant.