Key dates
| Deadline | What it is |
|---|---|
| 6 April 2026 | You can send the 2025/26 return from this date |
| 5 October 2026 | Last day to tell HMRC you need a return if you did not send one last year |
| 31 October 2026 | Paper return must arrive |
| 30 December 2026 | Online filing if you want the bill taken through your PAYE tax code |
| 31 January 2027 | Online return and balancing payment (11:59pm) |
| 31 July 2027 | Second Payment on Account, if you make them |
| 31 January 2028 | Online deadline for the 2026/27 return |
Payment on Account
If your last Self Assessment bill was over £1,000, HMRC collects two advance payments towards the next year: 31 January and 31 July, each usually 50% of that bill. First-time filers often meet this as "why is January 150% of what I expected?" It is a prepayment, not a penalty. You can ask HMRC to reduce it if this year's profit has fallen. Full walkthrough: payments on account explained.
Source: Payments on account.
Penalty ladder
Late filing and late payment are separate charges. What happens if you miss the deadline walks through both, including what to do today if you are already late.
| When | Late filing | Late payment |
|---|---|---|
| Day after the deadline | £100 (even if no tax is due) | — |
| 30 days late paying | — | 5% of unpaid tax |
| 3 months late filing | £10 a day, max £900 | — |
| 6 months | 5% of tax due or £300, whichever is greater | another 5% |
| 12 months | another 5% or £300 | another 5% |
Interest also runs on unpaid tax. Source: Self Assessment penalties.
Making Tax Digital dates
Separate from the January return. If your qualifying income (gross self-employment plus property, before expenses) was over £50,000, MTD for Income Tax applied from 6 April 2026. Over £30,000 from April 2027; over £20,000 from April 2028. Quarterly updates are not a tax payment. Check if it applies to you.
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