Who needs to file?
You need to send a Self Assessment tax return if, for example, you:
- are self-employed with more than £1,000 of income in the tax year
- are a partner in a business partnership
- rent out property and receive more than £1,000 in rent
- have other untaxed income, such as large amounts of savings interest or foreign income
- need to pay the High Income Child Benefit Charge and haven’t set it up through your tax code
GOV.UK has a short checker if you’re not sure.
The key dates for 2025/26
The 2025/26 tax year ran from 6 April 2025 to 5 April 2026.
| Date | What’s due |
|---|---|
| 5 October 2026 | Register for Self Assessment, if it’s your first return |
| 31 October 2026 | Paper tax return |
| 31 January 2027 | Online tax return, the tax still owed, and the first payment on account for 2026/27 |
| 31 July 2027 | The second payment on account for 2026/27 |
How payments on account work
HMRC asks you to pay towards next year’s bill in advance, in two halves, based on this year’s:
- 31 January: half of this year’s Income Tax and Class 4 National Insurance
- 31 July: the other half
Then, the following January, you pay any balancing payment (if you owe more than you paid in advance) along with the next first payment on account. If you paid too much, it’s knocked off or refunded.
You don’t need to make payments on account if your last bill was under £1,000, or if more than 80% of your tax was already taken at source, for example through PAYE on a job. Student loan repayments and Capital Gains Tax aren’t included in them.
Your first year: the big January bill
Say you start freelancing on 6 April 2026 and make £29,000 profit in 2026/27. Your bill for that year is about £4,272 (Income Tax and Class 4 National Insurance). Nothing is due until after the year ends, and then:
| Date | You pay | Amount |
|---|---|---|
| 31 January 2028 | The 2026/27 bill, plus the first payment on account for 2027/28 | £6,408 |
| 31 July 2028 | The second payment on account for 2027/28 | £2,136 |
- 31 January 2028 £6,408
- The 2026/27 bill £4,272
- First payment on account for 2027/28 £2,136
- 31 July 2028 £2,136
- Second payment on account for 2027/28 £2,136
The 2026/27 bill is £4,272 of Income Tax and Class 4 National Insurance. Nothing is due until the January after the tax year ends; then you also pay half of it again, in advance, towards 2027/28.
That first January catches many people out. Setting aside a share of every payment you receive, around 15% to 25% depending on your profit, makes it manageable. The self-employed tax calculator works out your bill and each payment date.
If your income is falling
Payments on account assume next year’s profit will be the same as this year’s. If you expect it to be lower, you can ask HMRC to reduce them, online or with form SA303. If you reduce them too far, you’ll pay interest on the difference, so only reduce what you’re confident about.
Penalties
Filing late (the return itself):
- £100 straight away, even if you owe no tax
- after 3 months, £10 a day, up to £900
- after 6 months and again after 12 months, 5% of the tax due or £300, whichever is more
Paying late (the tax): interest from the due date, plus 5% of the unpaid tax at 30 days, 6 months and 12 months.
If you can’t pay in full, you can often set up a payment plan online, which stops the late payment penalties.
Making Tax Digital
From 6 April 2026, sole traders and landlords with income over £50,000 must keep digital records and send HMRC quarterly updates through compatible software. The limit falls to £30,000 from April 2027. The tax return and payment dates above stay the same.
See your own numbers
The self-employed tax calculator shows your tax bill, whether you’ll need payments on account, and what’s due each January and July. With a job as well, it also works out the National Insurance cap: see National Insurance explained.