You need to file a Self Assessment return if HMRC sends you a notice to file, or if you have income or gains that PAYE has not dealt with, such as self employed income over £1,000, partnership profits, rental or dividend income above HMRC’s limits, a Capital Gains Tax bill or a High Income Child Benefit Charge you are not paying through PAYE. If you have never filed before, or did not need to file for the previous year, you must tell HMRC by 5 October after the end of the tax year.

Where does the legal duty to file come from?

There are two separate duties in the Taxes Management Act 1970, and confusing them causes most problems.

  • Notifying chargeability (section 7). If you are chargeable to Income Tax or Capital Gains Tax for a year and HMRC has not sent you a notice to file, you must tell HMRC within the notification period, which section 7(1C) sets at 6 months from the end of the tax year. That is why the deadline is 5 October.
  • Filing a return (section 8). Once HMRC gives you a notice under section 8, you must file a return for that year by the deadline, whether or not there is tax to pay.

Section 7(3) to (7) removes the duty to notify where all your income has been taxed under PAYE or at source, you have no chargeable gains and you owe no extra tax at higher rates. That is why most employees and pensioners never file a return.

What triggers a return for the 2025 to 2026 tax year?

gov.uk says you must send a return for the last tax year (6 April 2025 to 5 April 2026) if any of these applied:

  • you were self employed as a sole trader and earned more than £1,000 before deducting anything you can claim relief on;
  • you were a partner in a business partnership;
  • you had to pay Capital Gains Tax on something you sold or disposed of;
  • you had to pay the High Income Child Benefit Charge and do not pay it through PAYE;
  • you are an off payroll worker repaying a student or postgraduate loan.

HMRC’s online checker adds further triggers, including:

  • trust income on which you owe tax, or foreign income on which you owe UK tax;
  • holding certain positions, such as religious minister, Lloyd’s underwriter, examiner or invigilator, share fisher, or globally mobile employee on temporary secondment in the UK;
  • claiming more than £2,500 in employment expenses;
  • claiming more than £10,000 of tax relief under the Seed Enterprise Investment Scheme or Enterprise Investment Scheme (or both).

Being self employed triggers a return even if you have no tax to pay, the checker says.

What are the thresholds for untaxed income?

Untaxed income does not always mean a full return. gov.uk sets these limits:

Income Tell HMRC without a return Full return needed
Rental income Over £1,000 and up to £2,500 More than £2,500 after allowable expenses, or more than £10,000 before expenses
Trading income Not applicable Gross income over £1,000
Dividends Up to £10,000 Over £10,000
Savings interest Up to £10,000, if no tax calculation letter or Simple Assessment arrives by 31 March after the year Over £10,000
Other income such as tips or commission Up to £2,500 Over £2,500

The £1,000 trading and property allowances mean gross income of £1,000 or less from each source usually does not need reporting at all. For interest over £10,000, gov.uk says that where a bank reports this to HMRC, HMRC will send a notice to file. Our guides to the property income allowance and the Personal Savings Allowance explain how those allowances interact.

How does the High Income Child Benefit Charge fit in?

The charge applies where you or your partner receive Child Benefit and your adjusted net income is over £60,000. It claws back 1% of the benefit for every £200 over that figure, and all of it at £80,000. If both partners are over the threshold, the higher earner pays.

The charge used to be a common reason for employees to register. gov.uk now offers a PAYE route through the tax code, available only if you do not need a return for another reason and you register for the year on or before 31 January after it ends. If you are already in Self Assessment only for the charge, you can phone HMRC to leave Self Assessment and pay through PAYE instead. See our High Income Child Benefit Charge guide.

What if HMRC sends a notice to file?

gov.uk is clear: if HMRC asks you to send a return, you must do so by the deadline on the letter, even if you think you owe nothing. A late return starts with an initial £100 penalty.

If your circumstances have changed, for example you stopped trading, stopped letting or no longer pay the Child Benefit charge, tell HMRC as soon as possible using the online service, by phone or in writing. gov.uk warns that HMRC needs time to review the request before 31 January, and a penalty may apply if you leave it too late.

Under section 8B of the Taxes Management Act 1970, HMRC can withdraw a notice to file within 2 years of the end of the tax year (longer in exceptional circumstances), but not after you have filed the return. A withdrawal notice can also cancel late filing penalties already charged.

Do you need a return if HMRC sends a Simple Assessment?

Usually not. Section 7(2A) says that a person who receives a Simple Assessment for a year does not need to notify chargeability for that year unless they have income or gains that the assessment does not include. If the Simple Assessment misses something, the duty to notify still applies to the missing item.

Can you choose to file even if you do not have to?

Yes. gov.uk lists reasons to file voluntarily: proving self employment (for example for Tax Free Childcare or Maternity Allowance), paying voluntary National Insurance contributions and claiming relief on maintenance payments. A return is also the usual way to claim higher rate relief on Gift Aid; see claiming higher rate relief on Gift Aid.

What does this look like in practice?

Illustration only. Tom is employed on a salary taxed under PAYE. In the 2025 to 2026 tax year he also earned £1,800 from weekend photography and received £400 of dividends. The photography income is over the £1,000 trading allowance, so he is a sole trader who must file. He has never filed before, so he needed to register by 5 October 2026 and must file online by 31 January 2027. Once he files, the dividends go on the same return.

If Tom’s photography income had been £900, he would have had no trigger for a return, and the dividend income could have been reported to HMRC without filing.

What mistakes lead to penalties?

  • Assuming no tax means no return. A notice to file must be answered, and self employed people must file even with nothing to pay.
  • Missing 5 October. Registering late can lead to a failure to notify penalty if tax is still unpaid at 31 January. See registering for Self Assessment.
  • Ignoring a return that is no longer needed. If you stop trading and do not tell HMRC, notices keep arriving and penalties follow. Ask for withdrawal early.
  • Treating gross rent as profit. The £2,500 test for rental income is after allowable expenses, but the £10,000 test is before expenses.

For filing and payment dates, see Self Assessment deadlines and penalties.

If HMRC opens a check into your return, tax investigation insurance pays your accountant’s fees. Solar Protect cover pays up to £100,000 with no excess; it never pays tax, interest or penalties. Read how our cover works or get a quote.

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Sources

Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 8 October 2026. Part of Accountapedia, the Solar Protect guide to UK tax and accounting. This page is general information, not personalised advice.