Depending on your income and circumstances, you may need to register for self-assessment. This may be the case even if most of your income is taxed through PAYE.

You will usually need to file a self-assessment tax return if you are self-employed as a sole trader and your gross income exceeds £1,000 before expenses. Partners in business partnerships must also submit a self-assessment tax return.

A self-assessment tax return may also be required if your total taxable income exceeds £150,000 in the 2026-27 tax year, although people with lower income levels can still fall within self-assessment depending on their circumstances. This often applies where there is other untaxed income, such as rental income, foreign income, savings or investment income, including dividends.

Other common reasons for filing include paying Capital Gains Tax after selling assets or being liable to the High Income Child Benefit Charge. Although some smaller amounts of income relating to online selling or property income may be covered by allowances, it is important to check the position carefully.

If you need to complete a tax return for the first time, HMRC must generally be notified by 5 October following the end of the relevant tax year. For the 2026-27 tax year ending on 5 April 2027, the registration deadline will usually be 5 October 2027. HMRC also provides an online checker to help determine whether you need to file a return that can be found at www.gov.uk/check-additional-income-tax.

Taxpayers that need to complete a Self-Assessment return for the first time are required to notify HMRC. This is a final reminder that the latest date that HMRC should be notified, by new Self-Assessment taxpayers, for the 2022-23 tax year, is 5 October 2023. The deadline for filing the 2022-23 Self-Assessment tax return online and paying any tax due is 31 January 2024.

There are a number of reasons why you might need to complete a Self-Assessment return for the first time. This includes if you are self-employed, have an annual income over £100,000 and / or have income from savings, investment or property.

The £100,000 income threshold for Self-Assessment changed for taxpayers who are only taxed through PAYE. It increased from £100,000 to £150,000 with effect from 6 April 2023. However, the Self-Assessment threshold for 2022-23 returns remains at £100,000.  

HMRC has an online tool www.gov.uk/check-if-you-need-tax-return/ that can help you check if you are required to submit a Self-Assessment return.

The following list summarises some of the reasons when taxpayers are usually required to submit a Self-Assessment return:

• The newly self-employed (earning more than £1,000);
• Multiple sources of income;
• Taxpayers that have received any untaxed income, for example earning money for creating online content;
• Income over £100,000;
• earn income from property that they own and rent out;
• are a new partner in a business partnership;
• Taxpayers whose income (or that of their partner’s) was over £50,000 and one of you claimed Child Benefit;
• Receiving interest on savings or investment income of £10,000 or more before tax;
• Taxpayers who made profits from selling things like shares, a second home or other chargeable assets and need to pay Capital Gains Tax; and
• Taxpayers who are self-employed and earn less than £1,000 but wish to pay Class 2 NICs voluntarily to protect their entitlement to State Pension and certain benefits.