Who needs to send a Self Assessment tax return?

Scope: This guide helps individuals decide whether they may need a UK Self Assessment return for the tax year from 6 April 2025 to 5 April 2026 and what to do by 5 October 2026 if they are a new or returning filer.

The short answer

You must send a Self Assessment return if one of HMRC’s mandatory circumstances applies. These include being a sole trader with gross trading income over £1,000, being a partner in a business partnership, having Capital Gains Tax to pay on a disposal, having certain High Income Child Benefit Charge obligations not dealt with through PAYE, or being an off-payroll worker repaying a student or postgraduate loan.

Untaxed property income, tips, savings interest, dividends, foreign income and taxable UK income for a non-UK resident can also create a filing requirement depending on the facts.

If you are unsure, use HMRC’s official Self Assessment checker. Do not rely on an old income threshold or assume that PAYE means a return can never be required.

Circumstances that HMRC lists as requiring a return

For the last tax year, HMRC says a return is required if any of these applied:

• you were self-employed as a sole trader and your gross trading income was more than £1,000 before expenses or reliefs;
• you were a partner in a business partnership;
• you had Capital Gains Tax to pay when selling or otherwise disposing of an asset that had increased in value;
• you had to pay the High Income Child Benefit Charge and it was not paid through PAYE; or
• you were an off-payroll worker who was repaying a student or postgraduate loan.

This is a filing test, not a calculation of the tax due. For example, gross trading income is considered before business expenses, while the eventual taxable profit calculation is a separate step.

Untaxed income that may require a return

HMRC says a return may also be needed for untaxed income including:

• rent from property or land;
• tips and commission;
• savings interest;
• dividends and investment income;
• foreign income; and
• taxable UK income received by a non-UK resident.

The word “may” matters. The correct route can depend on the amount, the type of income, reliefs, residence status and whether HMRC can collect tax another way. Use the official checker rather than treating this list as a substitute for the decision service.

A quick decision path

1. Identify each source of income or gain for 6 April 2025 to 5 April 2026. Use gross figures where HMRC’s test asks for gross income.
2. Check the mandatory circumstances above. A partnership or chargeable disposal can matter even when there is no sole-trader income.
3. Consider untaxed income. Include property, investment and overseas sources rather than looking only at employment.
4. Use HMRC’s checker. Answer using the actual figures and circumstances for the relevant year.
5. Save the result and supporting records. If the result indicates a return, move to registration and deadlines.

Example: a small side activity

An employee receives £1,200 of gross income from regular paid services during 2025 to 2026 and incurs £350 of costs. HMRC’s mandatory sole-trader test looks at gross trading income before expenses, so the relevant figure for that test is £1,200, not the £850 left after costs.

Whether the activity is actually trading and how the profit should be calculated are separate questions. The official checker should be completed using the full facts.

When someone may choose to send a return

HMRC also identifies voluntary reasons, including proving self-employment for certain benefit claims, paying voluntary National Insurance contributions or claiming specified Income Tax relief. A voluntary return should have a clear purpose; filing one does not by itself prove that every figure or claim is correct.

The 5 October 2026 notification date

You must tell HMRC by 5 October 2026 if you need a return for 2025 to 2026 and either have not sent a return before, or registered before but did not need to send a return for 2024 to 2025. HMRC’s route for doing this is Self Assessment registration, which may include reactivating an existing account.

Missing 5 October does not remove the obligation. Register as soon as possible and continue working towards the filing and payment dates.

Common mistakes

• Using profit after expenses for HMRC’s £1,000 gross sole-trader test.
• Assuming an employee never needs Self Assessment.
• Ignoring property, savings, dividends, gains or foreign income because tax was deducted from salary.
• Filing solely because income exceeds an old general threshold that no longer appears in current HMRC eligibility guidance.
• Waiting until January to decide whether a first registration was required by 5 October.

What to do next

• Complete HMRC’s official checker.
• If a return is required, register for Self Assessment.
• Check every Self Assessment deadline for the 2025 to 2026 cycle.
• Gather records for every relevant income source and relief.
• If you no longer need to file but HMRC issued a notice, use HMRC’s route to tell it rather than simply ignoring the notice.