If you are self-employed or have income HMRC hasn't already taxed, you probably need to file a Self Assessment tax return. Here is who needs to file, the 2025/26 deadlines, how to do it, and how to avoid the penalties for getting it wrong.
Self Assessment is how HMRC collects tax on income that isn't taxed automatically through PAYE. If you are self-employed, run a small business, or have income from other sources, the responsibility is on you to report it and pay the right amount, on time. Miss the deadlines and the penalties start straight away, so it pays to know where you stand. This guide covers the essentials for sole traders and individuals across Bristol and the UK.
Do you need to file a Self Assessment tax return?
You will usually need to send a return for the 2025/26 tax year if any of the following applied:
- You were self-employed as a sole trader and earned more than £1,000 (before deducting expenses)
- You were a partner in a business partnership
- You had untaxed income, for example from renting out property, tips, commission, savings, investments, or dividends
- You needed to pay the High Income Child Benefit Charge
- HMRC otherwise asked you to complete a return
If your gross trading income was £1,000 or less, you usually don't need to file thanks to the trading allowance, though there are exceptions, such as wanting to claim a loss or pay voluntary Class 2 National Insurance. If you are unsure, it is worth checking rather than assuming.
The key deadlines for 2025/26
- 5 October 2026 — register for Self Assessment if it is your first time
- 31 October 2026 — deadline for paper tax returns
- 31 January 2027 — deadline to file online and pay any tax you owe
- 31 July — the second 'payment on account', if you make them
You can file your 2025/26 return any time from 6 April 2026. Filing early doesn't mean paying early, the tax is still due by 31 January 2027, but it tells you exactly what you owe with plenty of time to plan for it, rather than facing a surprise bill in January.
How to file
- Register with HMRC to get your Unique Taxpayer Reference (UTR) if you don't already have one
- Keep clear records of your income and expenses throughout the year
- Complete your return online (or on paper by 31 October)
- Pay what you owe by 31 January
- Or ask an accountant to prepare and file it for you, so nothing is missed
One important change to be aware of: if your combined self-employment and property income is over £50,000, you are now within Making Tax Digital for Income Tax, which began in April 2026. That replaces the single annual return with quarterly digital updates using compatible software, so the way you report is changing even if the tax itself isn't.
The cost of missing the deadline
- A £100 penalty as soon as you miss the filing deadline, even if you owe no tax
- Further penalties, including daily penalties, the longer a return stays unfiled
- Late-payment penalties of 5% of the unpaid tax at 30 days, 6 months, and 12 months
- Interest charged on any tax paid late, on top of the penalties
Getting help with your Self Assessment
A Self Assessment return is straightforward when your records are in order and you know what you can claim, but easy to get wrong under time pressure. We prepare and file Self Assessment tax returns for sole traders and individuals across Bristol and the UK, making sure every allowable expense is claimed and your return is accurate and filed well before the deadline. If you would rather take it off your plate, get in touch.
