Who needs to file a Self Assessment return?

Not everyone in the United Kingdom sends a Self Assessment return. Many employees have all of their Income Tax collected through PAYE and never see the 31 January deadline. The official “who must send a tax return” page lists the situations in which you must send one, and a separate official tool lets you check for the 2025/26 year. This guide summarises that list in our own words and then explains how registration and filing fit around it. It is general information, not a personal ruling; if HMRC has written to you asking for a return, you must send one.

The official “you must send a return” list

You must send a tax return if, in the last tax year (6 April to 5 April), any of the following applied. You were self-employed as a sole trader and earned more than £1,000 before taking off anything you can claim tax relief on. You were a partner in a business partnership. You had to pay Capital Gains Tax when you sold or disposed of something that increased in value. You had to pay the High Income Child Benefit Charge and do not pay it through PAYE. You are an off-payroll worker who is repaying a student or postgraduate loan.

The £1,000 sole-trader figure is a gross income test on that page, not a profit test. Someone with £1,200 of self-employed income and £400 of expenses is still over the line as official wording is written, even though taxable profit after expenses is lower. Trading allowance rules can affect the later tax calculation; they do not, on that list, replace the need to look carefully at whether you must notify HMRC.

Other reasons, including untaxed income

The same official page says you may also need to send a return if you have any untaxed income, and it gives examples: money from renting out a property or land; tips and commission; savings interest; dividends, including investments; foreign income; and any taxable UK income if you are a non-UK resident. “May” is the word HMRC uses there, which is why the official checker exists. Untaxed savings interest or a small amount of dividends does not automatically mean a return for every person, because banks often report interest and HMRC can collect some tax through a code. It does mean you should not assume silence is safe if the amounts are material or if you already know you are in Self Assessment.

You may also need to send a return if you want to claim tax relief on community investments or on some venture capital schemes. And you can choose to fill in a return to prove you are self-employed — for example to claim Tax-Free Childcare or Maternity Allowance — to pay voluntary National Insurance contributions, or to claim Income Tax relief on maintenance payments. Those last items are choices, not duties, but they still use the same filing service and the same deadlines once you are in the system.

How to check, and when to tell HMRC

If you are not sure, use the official “check if you need to send a Self Assessment tax return” tool for 2025/26 (6 April 2025 to 5 April 2026). That tool will not send your details to HMRC. If HMRC wrote to you asking you to send a return for that year, you must do so by the deadline on the letter. If you believe you no longer need to send a return, you need to contact HMRC and explain this; stopping on your own is not the same as HMRC taking you out of Self Assessment.

You must tell HMRC by 5 October if you need to complete a return for the previous year and you have either not sent a return before, or you registered before but did not need to send a return for 2024/25. You can tell HMRC by registering. The previous tax year, for the 5 October 2026 date, is the year that ended on 5 April 2026. If you tell HMRC after 5 October 2026 you could get a penalty, and a failure-to-notify charge can arise if tax is still unpaid on 31 January. The deadlines guide sets out the filing and payment dates that follow registration.

What filing involves, and what it does not

Sending a return is how you report the income and claims that sit on the official list. It is not, by itself, a request for paid software. You can file online for free on GOV.UK if you are self-employed, or if you are not self-employed but still send a return — for example because you receive income from renting out a property. You will need a Unique Taxpayer Reference and a way to sign in. The official service cannot be used for every type of return; partnerships, some trusts, some non-resident cases and a few other groups are told to use commercial software or other forms instead.

Our tools can help you estimate Income Tax, Class 4 National Insurance, payments on account or a student loan repayment before you file. They cannot tell you, with certainty, whether you must file. That question belongs with the official list, the official checker, and any letter HMRC has already sent. If you are on the list, register in time, keep records, and file by the deadline that applies to you.

Capital gains, Child Benefit, and student loans on the official list

Having to pay Capital Gains Tax is an official “must send a return” reason, even if you have no self-employment at all. Selling a second home, or some share disposals, can put you in Self Assessment for that reason alone. The gain is reported on the return; it is not part of payments on account, and it is not something our Income Tax calculator estimates. Official Capital Gains Tax pages, and the return itself, are the places for those figures.

The High Income Child Benefit Charge appears on the same list if you have to pay it and you do not pay it through PAYE. From 2024/25 the official income threshold for that charge is £60,000. Paying the charge is not optional once it applies, but you can sometimes choose PAYE rather than a return if the charge is your only reason for being in Self Assessment and you contact HMRC in time. Our Child Benefit charge guide restates those official thresholds without trying to compute the clawback.

Off-payroll workers who are repaying a student or postgraduate loan are also on the official “must send” list. That is a narrower group than every graduate who makes repayments through PAYE. If you are unsure whether the off-payroll rule applies, official IR35 and off-payroll guidance is the place to look, and the official checker is still worth running. Do not rely on a third-party summary — including this one — if your working arrangements are unusual.