What Is Self Assessment and Who Needs to File a Tax Return?
Tax year: 2026/27 | Last reviewed: 2 October 2026
Self Assessment is the system HMRC uses to collect Income Tax and National Insurance that has not already been taken through PAYE. Around 12 million people file a return every year. If you are employed and have no other income, you probably do not need to. If you have income from self-employment, property, investments or abroad, you probably do.
You normally need to file if you
- Were self-employed and your gross trading income was more than £1,000 (the trading allowance)
- Were a partner in a business partnership
- Received rental income above £1,000 before expenses, unless HMRC has agreed to collect a small amount through your tax code
- Had Child Benefit and you or your partner had adjusted net income over £60,000, unless you have chosen to pay the High Income Child Benefit Charge through PAYE
- Received untaxed income, for example tips, commission or income from online platforms
- Had dividends over £10,000 or savings interest HMRC cannot collect through your tax code
- Sold assets such as shares, crypto or a second home and made a gain that needs reporting (UK residential property gains also need a separate 60-day return)
- Had foreign income or gains, or you need to claim tax relief on overseas income
- Want to claim relief on pension contributions or Gift Aid as a higher or additional rate taxpayer
Who usually does not need to file
- Employees and pensioners whose tax is all collected through PAYE, even if their income is over £150,000 (this threshold was removed from 2023/24)
- People whose only extra income is under the £1,000 trading or property allowances
- Company directors with only salary and modest dividends, where HMRC has not issued a notice to file
If HMRC sends you a notice to file, you must file or ask HMRC to withdraw it. Ignoring a notice leads to penalties even if no tax is owed.
How to register
If you need to file for the first time, register by 5 October after the end of the tax year. For 2025/26 that was 5 October 2026. Self-employed people register for Self Assessment and Class 2/Class 4 NI together. Others, such as landlords, use a separate form. HMRC then posts your Unique Taxpayer Reference (UTR), which you need to file. Registering late can lead to a failure to notify penalty if tax is owed, so if you have missed the date, register straight away.
What goes on the return
The main return (SA100) covers employment income, interest, dividends, pension contributions and Gift Aid. Extra pages cover self-employment, partnerships, property, foreign income, capital gains and residence. Your tax is then calculated across all your income, which is why things like the £100,000 Personal Allowance taper often only show up on a return.
Deadlines
- Paper return: 31 October after the tax year
- Online return and payment: 31 January after the tax year (31 January 2027 for 2025/26)
- Second payment on account: 31 July
See our guide to the 31 January 2027 deadline for a full checklist.
Making Tax Digital is changing Self Assessment
From 6 April 2026, sole traders and landlords with qualifying income over £50,000 must keep digital records and send quarterly updates through software, with the threshold falling to £30,000 in April 2027 and £20,000 in April 2028. The annual return still exists but is filed through MTD software. Check where you stand with our MTD readiness checker.
FAQs
Do I need to file if I earn over £100,000?
Not automatically. If all your income is taxed through PAYE and your tax code is right, you may not need to. Many people over £100,000 still file to claim pension relief and restore their Personal Allowance.
Do I need a return for a small side hustle?
If your gross income from it was £1,000 or less in the tax year, you normally do not. Above that, you need to register and file.
Can an accountant file for me?
Yes. Once you authorise us as your agent we can see your HMRC record, prepare the return and file it. See our tax return service.
Talk it through with Digivolve
Not sure whether you need to file? Tell us about your income and we will confirm in plain English, then handle registration and the return if one is needed.
This article is general information based on the rules for the 2026/27 tax year as at October 2026. It is not personal tax advice. Rates and thresholds can change, so please speak to us before acting.