The dates that catch self-employed people out
Being self-employed means the tax calendar is now your responsibility — nobody's operating PAYE in the background for you. HMRC's penalties for missing deadlines are automatic: a missed filing gets you an instant £100 fine even if you owe no tax, and late payments rack up interest. None of it is complicated, but all of it is unforgiving if you forget.
The good news: there are really only a handful of dates to know, and once you've got them in your diary the whole thing runs on rails. This guide lays out the full calendar — registering when you start, the January filing deadline, payments on account, and the new Making Tax Digital quarterly reporting that begins in April 2026.
What this guide covers
- The deadline to register for Self Assessment when you start out
- The 31 January filing and payment deadline explained
- How payments on account work and when they're due
- What MTD for Income Tax means for your dates from April 2026
The UK tax year
First, the frame everything hangs off: the UK tax year runs from 6 April to 5 April. When people say "the 2025/26 tax year" they mean 6 April 2025 to 5 April 2026. Every deadline below refers back to that year.
When you first go self-employed: register by 5 October
If you start working for yourself, you must tell HMRC and register for Self Assessment by 5 October following the end of the tax year you started. So if you began trading during the 2025/26 year, your deadline to register is 5 October 2026. Register late and you can be penalised, so do it early — you don't have to wait.
The £1,000 trading allowance. If your total self-employed income for the year is £1,000 or less, you generally don't need to register or report it — the trading allowance covers it. Go over £1,000 and the normal rules apply. It's a genuine income figure, not profit.
31 January: the big one
The 31 January after the end of the tax year is the deadline for two things at once:
- Filing your online Self Assessment tax return for the year that ended the previous 5 April.
- Paying any tax you owe for that year (your "balancing payment").
So for the 2025/26 tax year, you file and pay by 31 January 2027. If you still file on paper rather than online, that deadline is earlier — 31 October — which is one of several reasons almost everyone files online now.
Payments on account: 31 January and 31 July
This is the part that surprises people in their first proper year. If your Self Assessment bill is more than £1,000, HMRC asks you to pay towards next year's tax in advance, in two instalments called payments on account:
- First payment on account: 31 January (alongside your balancing payment).
- Second payment on account: 31 July.
Each instalment is normally half of your previous year's tax bill. When you finally file, HMRC compares what you actually owe against what you've paid on account and either bills you the balance or refunds the difference.
Worked example — the first-year squeeze. Suppose your 2025/26 tax bill comes to £4,000. On 31 January 2027 you don't just pay £4,000 — you also pay a first payment on account of £2,000 towards 2026/27. That's £6,000 in one go. Then on 31 July 2027 you pay the second £2,000. This is why new sole traders should set money aside from every invoice — the first January can be a shock if you haven't. Put roughly 25–30% of your profit aside as you go and you'll be fine.
National Insurance and income tax rates to plan around
So you know what you're setting aside for: for 2025/26 the personal allowance is £12,570, income tax is 20% up to £50,270, 40% up to £125,140 and 45% above that. On top of income tax, self-employed profits attract Class 4 National Insurance at 6% between £12,570 and £50,270, then 2% above (check the current rates — they move). Class 2 NI has effectively been abolished, so there's no separate weekly stamp to worry about for most people.
Making Tax Digital for Income Tax — new from April 2026
This is the big change on the horizon. Making Tax Digital (MTD) for Income Tax replaces the once-a-year return with quarterly digital updates sent to HMRC through compatible software, plus a final year-end declaration. It's being phased in by income level:
- From 6 April 2026 — if your self-employment and/or property income is over £50,000.
- From April 2027 — over £30,000.
- From April 2028 — over £20,000.
If you're caught by MTD you'll need to keep digital records and file quarterly, which means the days of the shoebox of receipts once a year are ending. It's less scary than it sounds once you've got software set up — but it does mean thinking about this now if your income is above £50,000.
Your one-page diary
- 5 October — register for Self Assessment (first year only).
- 31 January — file online return, pay balancing payment + first payment on account.
- 31 July — second payment on account.
- From 6 April 2026 — quarterly MTD updates if you're over the income threshold.
If you're in construction, these dates sit alongside your CIS deductions and refund, and if your turnover is climbing you'll want to keep an eye on VAT registration too — VAT returns have their own quarterly deadlines on top of all this.
Juggling filing, two payments on account and now quarterly MTD updates is exactly where a lot of self-employed people slip up. If you'd rather have someone keep the calendar, file on time and make sure you're not overpaying, get started with us and we'll take the dates off your plate.
