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.

There are a number of reasons why you might need to complete a self-assessment tax return. This includes if you are self-employed, a company director, have an annual income over £150,000 and / or have income from savings, investment or property.

The £100,000 self-assessment threshold changed for taxpayers taxed through PAYE only. The limit increased from £100,000 to £150,000 with effect from 6 April 2023.

Taxpayers that need to complete a self-assessment return for the first time should inform HMRC as soon as possible. The latest date that HMRC should be notified is by 5 October following the end of the tax year for which a self-assessment return needs to be filed.

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.

You are required to submit a self-assessment return if any of the following apply:

• you were self-employed as a ‘sole trader’ and earned more than £1,000 (before deducting items available for tax relief);
• you were a partner in a business partnership;
• you received a total taxable income of more than £150,000 in 2023-24 (£100,000 in 2022-23);
• you were obliged to pay Capital Gains Tax when you sold or ‘disposed of’ an asset that increased in value; or
• you had to pay the High Income Child Benefit Charge.

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

• money from renting out a property
• tips and commission
• income from savings, investments and dividends
• foreign income