Quick answer: You normally need to file a Self Assessment return if you were self-employed and earned more than £1,000 before expenses, were a partner in a partnership, owe the High Income Child Benefit Charge, or HMRC sent you a notice to file. Employees taxed through PAYE with no other income often do not. The only official way to be sure is the free GOV.UK checker.
This guide lists the common reasons people have to file. It is a starting point, not a ruling: thresholds change, and the right answer depends on your whole tax position. Check anything that matters on GOV.UK before you rely on it. If you’re self-employed or a landlord, our Making Tax Digital checker shows when you’ll also need to send quarterly updates.
Common reasons you need to file
- Self-employed as a sole trader with gross income (before expenses) over £1,000 in the tax year. HMRC includes income from trading or providing services online.
- A partner in a business partnership.
- The High Income Child Benefit Charge applies to you. This depends on you or your partner’s income and on claiming Child Benefit, so check the current threshold on GOV.UK.
- Rental income. Third-party guides give a figure of more than £2,500 in untaxed rental income as a trigger. Check the current figure on GOV.UK.
- HMRC told you to. If you get a notice to file, you must file even if you think you owe nothing.
Other situations to check
Higher incomes, untaxed dividends or interest, foreign income, and selling assets can also lead to a return. The figures vary and change, so use the GOV.UK checker rather than a number from a blog, including this one.
If you are not sure, you can still check in minutes
The GOV.UK checker asks a short series of questions and does not send your details to HMRC. Make sure it is set to the 2025 to 2026 tax year, which runs from 6 April 2025 to 5 April 2026.
What to do if the answer is yes
- If you are new to Self Assessment, register with HMRC now. The 5 October 2026 registration date has passed, so do it straight away to limit any late-notice penalty.
- Note the dates in our 31 January 2027 deadline guide.
- Gather your records. Our spreadsheet maker can total income and expenses by category.
- Check whether you will owe payments on account with our calculator.
- Making Tax Digital for Income Tax is separate and starts from April 2026 for some people; see the MTD checker.
Altto is not affiliated with HMRC. This is general information, not tax advice.
Sources
The thresholds and triggers in this guide come from HMRC’s own guidance, checked on 16 October 2026:
- GOV.UK — Check if you need to send a Self Assessment tax return (the official checker; it covers the 2025 to 2026 tax year and does not send your details to HMRC)
Figures that GOV.UK changes from year to year are deliberately left to that page rather than copied here.
Frequently asked questions
Do I need to file a tax return if I earn under £1,000 self-employed?
Do employees need to file a Self Assessment return?
What if HMRC sends me a notice to file?
Where can I check for certain?
Need tidy records before you file?
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Altto is not affiliated with HMRC. This is general information, not tax advice.