Self Assessment deadlines and payments on account.
The dates that matter for 2026/27, why your first bill is bigger than you expect, and what happens if you're late.
Updated October 2026
The key dates — 2026/27 tax year
| Date | What happens |
|---|---|
| 6 April 2026 | Tax year starts |
| 5 April 2027 | Tax year ends |
| 5 October 2027 | Register for Self Assessment if you're new to self-employment |
| 31 October 2027 | Paper return deadline |
| 31 January 2028 | Online return deadline · pay tax owed · first payment on account |
| 31 July 2028 | Second payment on account |
What is a payment on account?
If your Self Assessment bill is more than £1,000 (and less than 80% of your tax was already collected at source), HMRC asks you to pay next year's tax in advance, in two equal instalments — 31 January and 31 July. Each is half of the previous year's bill.
Example
Your first-year bill is £4,000.
| When | What you pay |
|---|---|
| 31 January | £4,000 (this year's bill) + £2,000 (first payment on account) = £6,000 |
| 31 July | £2,000 (second payment on account) |
That's why the first January bill feels like 1.5 times your tax. After that, the payments on account roughly smooth things out — and if your income drops, you can ask HMRC to reduce them. Our tax calculator shows your likely January bill.
Penalties for filing late
- 1 day late: £100 — even if you owe nothing
- 3 months late: daily penalties of £10, up to 90 days (£900)
- 6 months late: the greater of 5% of the tax due or £300
- 12 months late: another 5% or £300, whichever is greater
Paying late adds interest and further penalties. If you've missed a deadline, act now: file and pay as soon as you can.
Making Tax Digital changes the rhythm
If your income is over £50,000 you'll send quarterly updates instead — see Making Tax Digital.
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