Self Assessment 2025–26: every date between now and 31 January 2027
For the 2025–26 tax year, the online return and the tax owed are both due by 11:59pm on 31 January 2027. A paper return is due by 31 October 2026. File online by 30 December 2026 if you want a bill under £3,000 collected through your tax code instead.
Last updated 25 Sep 2026 · Neos Technologies Ltd
Who this is for: anyone filing a Self Assessment return for the tax year 6 April 2025 to 5 April 2026 — sole traders, landlords, company directors with untaxed income, and anyone HMRC has asked to file.
Who it is not for: trustees and non-resident companies, whose paper deadline is different, or anyone asking about Making Tax Digital quarterly updates, which have their own dates.
| Date | What it is | Source |
|---|---|---|
| 5 October 2026 | Tell HMRC if you need to file a return for 2025–26 and have not filed one before. | GOV.UK |
| 31 October 2026 | Paper returns must reach HMRC by 11:59pm. | GOV.UK |
| 30 December 2026 | File online by 11:59pm to have a bill under £3,000 collected through your tax code, if you already pay tax through PAYE. | GOV.UK |
| 31 January 2027 | Online returns due by 11:59pm. Pay what you owe for 2025–26, and your first payment on account for 2026–27 if you make them. | GOV.UK, payments on account |
| 1 February 2027 | A return not yet filed gets an initial £100 penalty. | GOV.UK |
| 30 days after 31 January | Tax still unpaid gets a penalty of 5% of the unpaid amount, and interest keeps running. | GOV.UK |
| 3 months after 31 January | A return still not filed starts to cost £10 a day, up to £900. | GOV.UK |
| 31 July 2027 | Second payment on account for 2026–27. It is also six months after the deadline, when a return still not filed costs a further 5% of the tax due or £300, whichever is greater, and unpaid tax another 5%. | GOV.UK, penalties |
Payments on account: why January can cost more than you expect
If your last Self Assessment bill was £1,000 or more, and less than 80% of your tax was already taken at source, HMRC asks for two payments on account towards next year’s bill: one on 31 January and one on 31 July. So 31 January 2027 can carry two amounts — the balance for 2025–26 and the first half of an estimate for 2026–27. It is the second one that people leave out of the plan.
Three weeks is the useful warning
Most of the work in a return is finding things: the P60, the bank interest, the rental statements, the pension contributions. None of that can start on 30 January. A reminder that arrives with weeks to spare is one you can act on; one that arrives on the day is just a warning about a penalty.
What Radar does with this
- Life setup asks: “Do you file a Self Assessment tax return?” The online deadline is 31 January. Radar reminds you two months ahead. Radar reminds you 60 days ahead.
- You can put the 30 December date on your Radar too, if you want the bill collected through your tax code: it is just a commitment with a date.
Radar reads the calendars, task lists and CRM you connect, and the dates you give it. It writes back only when you press a button, and it never sends anything by itself.
Limitations and status
- Radar does not connect to HMRC, file your return or work out your tax. It reminds you of the date you give it and shows it beside everything else that is closing in.
- These dates are for the 2025–26 tax year. Trustees and non-resident companies have a different paper deadline.
- Penalty amounts are HMRC’s, as published on GOV.UK when this page was written. HMRC’s own pages are the ones to rely on.
Questions
When is the Self Assessment deadline for 2025–26?
The online return and the payment are both due by 11:59pm on 31 January 2027. Paper returns are due by 31 October 2026. (GOV.UK)
What happens if I miss 31 January?
An unfiled return gets an initial £100 penalty, then £10 a day after three months, up to £900, then more at six and twelve months. Unpaid tax gets 5% penalties at 30 days, six months and twelve months, plus interest. (GOV.UK)
Can I pay through my tax code instead?
Yes, if you owe less than £3,000, already pay tax through PAYE, and file online by 30 December 2026 or on paper by 31 October 2026. (GOV.UK)
Do I have to make payments on account?
Not if last year’s bill was less than £1,000, or if more than 80% of the tax you owed was already paid outside Self Assessment, for example through your tax code. (GOV.UK)
Sources
- Self Assessment tax returns: deadlines, read 25 Sep 2026
- Self Assessment tax returns: penalties, read 25 Sep 2026
- Understand your Self Assessment bill: payments on account, read 25 Sep 2026
- Pay your Self Assessment bill through your tax code, read 25 Sep 2026
Written by Neos Technologies Ltd · first published 25 Sep 2026. Radar is made by Neos Technologies Ltd.