YF Accounting6 min read
You need to file a Self Assessment tax return for the 2025/26 tax year if any of these applied to you between 6 April 2025 and 5 April 2026: you were self-employed and earned more than £1,000, you were a partner in a business, you owed Capital Gains Tax, you had to pay the High Income Child Benefit Charge, or you had untaxed income that HMRC cannot collect through your tax code. If one of those fits, you must tell HMRC by 5 October 2026 and file online by 31 January 2027. This guide walks through who has to file, who does not, and the dates that matter.
Who has to file a tax return
HMRC sets out clear triggers. If any of the following applied during the last tax year, a return is not optional:
- You were self-employed as a sole trader and your gross income was 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 after selling or giving away something that went up in value, such as a second property or shares.
- You had to pay the High Income Child Benefit Charge and do not pay it through your tax code.
- You are an off-payroll worker repaying a student or postgraduate loan.
The self-employment trigger is the one most people meet. The £1,000 figure is your gross income, not your profit, so a side trade that turned over £1,200 still counts even if your costs left you with very little to keep.
The grey areas that catch people out
Plenty of people owe a return without ever thinking of themselves as self-employed. You may need to file if you had untaxed income that HMRC has not already taken tax from at source. Common examples include:
- Rent from a property you let out.
- Tips and commission that have not been taxed.
- Income from savings, investments and dividends above your allowances.
- Foreign income.
Two situations trip people up more than any other. The first is the side hustle. If you sold online, took on freelance work or rented out a room and your gross income from it passed £1,000, you are into Self Assessment territory even if it never felt like a real business. The second is the High Income Child Benefit Charge. If you or your partner claim Child Benefit and one of you has an adjusted net income above £60,000, some of it has to be paid back. The charge is 1% of your Child Benefit for every £200 you earn over £60,000, and once income reaches £80,000 the whole amount is clawed back. If you do not pay this through your tax code, you have to file a return to settle it.
Who does not need to file
If your only income is a salary or pension that is already taxed under PAYE, and you have no untaxed income to declare, you usually do not need to file at all. The same is true of a small side trade whose gross income stays at or below the £1,000 trading allowance, since that income is covered by the allowance and does not need reporting. Savings and dividend income that sits within your Personal Savings Allowance and Dividend Allowance is also dealt with automatically in most cases. If you are genuinely unsure, it is far safer to check than to assume.
The deadlines you cannot miss
For the 2025/26 tax year the dates to keep in front of you are:
- 5 October 2026: the deadline to tell HMRC you need to file, if you have never filed before or did not need to last year. You do this by registering for Self Assessment.
- 31 October 2026: the deadline for a paper return.
- 30 December 2026: file online by this date if you want HMRC to collect a smaller bill through your tax code rather than as a lump sum.
- 31 January 2027: the deadline to file your online return and to pay any tax you owe for 2025/26.
If you register after 5 October 2026, HMRC will give you a later filing date of three months from the date on its letter or email, but you still have to pay what you owe by 31 January 2027 to avoid interest and penalties.
What happens if you file late
Miss the filing deadline and the penalties build quickly. You get an automatic £100 penalty the moment your return is late, even if you owe no tax at all. After three months, daily penalties of £10 start to stack up to a maximum of £900. At six months a further charge of 5% of the tax due or £300 is added, whichever is greater, and the same again at twelve months. Late payment carries its own penalties of 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest on top. Filing on time, even with an estimate you correct later, is almost always cheaper than missing the date.
How to check if you are still not sure
HMRC has a free online tool that walks you through a short set of questions and tells you whether you need to send a return for 2025/26. It does not pass your answers on to HMRC, so it is a safe first step. You can find it by searching for “check if you need to send a Self Assessment tax return” on gov.uk. If your situation is more involved, with a mix of employment, a side trade and some investment income for example, it is worth getting a second opinion before the registration deadline rather than after it. Our Self Assessment guide sets out the whole process from registering to filing.
Frequently asked questions
I am employed and pay tax through PAYE. Do I still need to file?
Usually not, if your salary is your only income and it is all taxed under PAYE. You would only need to file if you also had untaxed income to declare, owed the High Income Child Benefit Charge, or had a Capital Gains Tax bill. Being an employee does not by itself rule you out of Self Assessment.
I made under £1,000 from a side hustle. Do I report it?
No. The £1,000 trading allowance means that if your gross income from self-employment or casual work was £1,000 or less for the year, you do not need to tell HMRC or file a return for it. Once you go over £1,000 gross, you do need to register and report it.
What if I need to file but have never registered before?
You must register for Self Assessment by 5 October 2026 for the 2025/26 tax year. Registration gives you a Unique Taxpayer Reference, which you need before you can file. Leave it too late and you can run into a failure to notify penalty on top of any late filing charge, so it is worth doing as soon as you know you are in scope.
I owe no tax. Do I still have to file if HMRC asked me to?
Yes. If HMRC has issued you a notice to file, you must submit the return even if the result is a nil bill. The £100 late filing penalty applies whether or not you owe anything. If you genuinely no longer need to file, contact HMRC to have the return requirement removed rather than simply ignoring it.
Can YF Accounting work out whether I need to file and handle it for me?
Yes. We look at your full picture, tell you clearly whether a return is needed for 2025/26, and if it is, we register you, prepare the return and file it so the deadlines are covered. You can book a free call and we will let you know exactly where you stand.
Not sure where you stand? Get in touch with YF Accounting and we will tell you whether you need to file before the deadline comes around.
Founder of YF Accounting — a fixed-fee, fully digital accountancy practice in Manchester serving SMEs, sole traders and landlords across the UK. One point of contact, unlimited support, no surprise bills.
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