Register by 5 October
You must tell HMRC by 5 October after the end of the tax year you need to file for. The tax year that ended on 5 April 2026 is the 2025/26 tax year, so if that's your first year of trading and you haven't sent a return before, you need to register by 5 October 2026. Tell HMRC by registering for Self Assessment, which gives you a Unique Taxpayer Reference (UTR) you'll need to file.
If you tell HMRC after 5 October 2026, you could get a penalty. If that happens to you, HMRC will send a letter or email with a different filing deadline, three months from the date on it, but your payment deadline of 31 January 2027 doesn't move. Register as soon as you can, even if you're past the date.
If you're not sure whether you need to register at all, see our guide to becoming a UK sole trader, which covers who needs to file and when.
The key dates for 2025/26
If you started trading during the 2025/26 tax year (6 April 2025 to 5 April 2026), these are the dates that apply to your first return:
| Date | What's due |
|---|---|
| 5 October 2026 | Register for Self Assessment, if you haven't already. |
| 31 October 2026 | Deadline for a paper tax return, if you file on paper instead of online. |
| 30 December 2026 | Last date to file online if you want any tax you owe collected through your PAYE tax code instead of paid directly (only an option in some circumstances). |
| 31 January 2027 | Deadline for an online tax return, and the date any tax you owe for 2025/26 is due. |
| 31 July 2027 | Second payment on account for 2026/27, if you need to make one (see below). |
Nearly everyone files online rather than on paper these days, since it gives you three extra months. Whichever way you file, HMRC must receive it by the deadline, not just have it in the post.
Payments on account explained
Payments on account are advance payments towards your next year's tax bill, so HMRC collects roughly what you'll owe in two instalments rather than one large sum a year behind. You don't have to make them if either last year's tax bill was under £1,000, or more than 80% of it was already collected another way, for example through a PAYE tax code.
If you do need to make them, each payment is half of the tax you owed the previous year, due by 31 January and 31 July.
A worked example. Say your 2025/26 tax bill comes to £3,000, and you didn't make any payments on account last year, since this is your first return. By 11:59pm on 31 January 2027 you'd owe your full £3,000 bill for 2025/26, plus a first payment on account of £1,500 (half of £3,000) towards your 2026/27 bill. That's £4,500 due on 31 January 2027. You'd then pay a second instalment of £1,500 on 31 July 2027.
If your actual 2026/27 tax turns out to be more than the £3,000 you've paid on account, you'll owe a top-up "balancing payment" the following 31 January. If it's less, you can ask HMRC to reduce your payments on account, or claim a refund once you've filed.
The practical upshot: set aside more than just your headline tax bill in your first year, because the first 31 January after you start trading can ask for one and a half times what you actually owe. Our free pricing calculator estimates your income tax and National Insurance so you can plan ahead.
How long to keep your records
You must keep your business records for at least 5 years after the 31 January submission deadline of the tax year they relate to, in case HMRC checks them. For your 2025/26 return, filed by 31 January 2027, that means keeping everything until at least the end of January 2032.
If you file more than 4 years after the deadline, you only need to keep records for 15 months after you actually send the return. Either way, it's simplest to just keep everything for the full 5 years as a habit, including invoices, receipts and bank statements.
Making Tax Digital for Income Tax
Most new sole traders don't need to think about this yet. Making Tax Digital for Income Tax means keeping digital records and sending quarterly updates instead of one annual return, and it only applies once your qualifying income from self-employment and property goes over a threshold: £50,000 from April 2026, £30,000 from April 2027, and £20,000 from April 2028. HMRC works out whether you're over the threshold from an earlier tax year's return and writes to tell you if you need to join. If you're well under these figures in your first year, carry on filing Self Assessment as normal.
Check what your rate leaves you with
Our free pricing calculator estimates the income tax and National Insurance on any rate you put in, so you can see roughly what you'll owe before the payments on account catch you out.
Free Pricing Calculator
See roughly what you'd keep after tax before you quote a client. No sign-up, and nothing is uploaded.
Open the calculator →Sole Trader Starter Pack, £19
Has a self-assessment checklist and deadline planner with the key dates from this guide, and five other files.
See what's inside →Common first-return questions
When do I have to register for Self Assessment?
By 5 October after the end of the tax year you need to file for. For the 2025/26 tax year (6 April 2025 to 5 April 2026), that's 5 October 2026. If you tell HMRC after that date, you could get a penalty.
What if I register after 5 October?
HMRC will write or email you with a different deadline to send your return by, which is 3 months from the date on that letter or email. You still have to pay any tax you owe by 31 January, so register as soon as you can.
What are payments on account?
Advance payments towards your next tax bill, each one half of the tax you owed last year, due on 31 January and 31 July. You don't pay them if last year's tax was under £1,000, or if more than 80% of it was already collected at source.
How long do I need to keep my records?
At least 5 years after the 31 January submission deadline of the tax year they relate to. For a 2025/26 return filed by 31 January 2027, keep your records until at least the end of January 2032.
Does Making Tax Digital for Income Tax affect me yet?
Only if your qualifying income from self-employment and property is over the threshold for that tax year: £50,000 from April 2026, £30,000 from April 2027, and £20,000 from April 2028. Below that, keep filing Self Assessment as normal.
This is general information, not tax advice. Sources: GOV.UK, Check how to register for Self Assessment; GOV.UK, Self Assessment tax returns: Deadlines; GOV.UK, Understand your Self Assessment tax bill: Payments on account; GOV.UK, Business records if you're self-employed: How long to keep your records; GOV.UK, Find out if and when you need to use Making Tax Digital for Income Tax. Figures correct as of September 2026.