This free checker asks up to 9 questions to indicate whether you need to register for Self Assessment for the 2025-26 tax year. The most common trigger is gross trading income over £1,000; new registrants must sign up with HMRC by 5 October 2026 and file by 31 January 2027.
Who must send a Self Assessment tax return?
You normally need a return for the 2025-26 tax year if any of the following applied between 6 April 2025 and 5 April 2026: you were self-employed with gross trading income over £1,000; you were a partner in a business partnership; your total taxable income exceeded £150,000; you had Capital Gains Tax to pay; you or your partner received Child Benefit while the higher earner's income exceeded £60,000 and the charge is not being collected through PAYE; you had rental profit of £2,500 or more or gross rental income of £10,000 or more; or you had untaxed income such as savings interest or dividends over £10,000, foreign income, or tips and commission. HMRC can also simply require a return by sending a notice to file, which must be completed or formally withdrawn regardless of the list above.
What does not require a tax return?
Income already fully taxed through PAYE, with nothing on the list above, does not require a return. The £1,000 trading allowance means small side hustle income needs no declaration at all, and selling unwanted personal belongings is not trading. Savings interest is usually collected automatically through the Personal Savings Allowance and tax code adjustments below £10,000. Rental profit between £1,000 and £2,500 sits in a middle category: HMRC must be told, but a full return is not always needed. Anyone who filed last year but no longer meets any criterion should tell HMRC rather than simply not filing, because an expected return that never arrives attracts automatic penalties even when no tax is owed.
Key Self Assessment dates for 2025-26
Registration deadline for new entrants: 5 October 2026. Paper return deadline: 31 October 2026. Online return and payment deadline: 31 January 2027. Payments on account, where they apply, fall due on 31 January and 31 July. Missing the filing deadline triggers an automatic £100 penalty, with daily penalties after three months.
Is this checker official?
No. This is an independent editorial tool summarising GOV.UK rules for the 2025-26 tax year. It gives an indication only. Confirm your position with the official HMRC checker or a qualified adviser before acting.
Does the £1,000 threshold include expenses?
No. The trading allowance tests gross income, meaning total takings before any expenses are deducted, combined across all trading activities in the tax year.
What if HMRC sent a notice but nothing on the list applies?
A notice to file must still be dealt with. Either complete the return or contact HMRC and ask for the notice to be withdrawn; ignoring it leads to penalties even where no tax is due.
Can the Child Benefit charge be paid without a return?
Since 2025, some employed people can have the High Income Child Benefit Charge collected through their PAYE tax code instead of filing. Anyone not paying it that way still needs Self Assessment.
When must UK property gains be reported?
Gains on UK residential property must be reported and the tax paid within 60 days of completion using HMRC's property reporting service, separately from any annual return.
Disclaimer: This tool and page are for information only and do not constitute tax advice. Thresholds relate to the 2025-26 tax year and can change. Verify with GOV.UK or a qualified adviser before making decisions.
Sources
- GOV.UK: who must send a tax return – accessed 21 July 2026
- GOV.UK: check if you need to send a Self Assessment tax return – accessed 21 July 2026
- HMRC press release, 21 July 2026 – accessed 21 July 2026