The online filing deadline for your 2025/26 Self Assessment tax return is 31 January 2027. Any tax owed for 2025/26 — and your first payment on account for 2026/27, if you make them — is due the same day. File late and HMRC charges an automatic £100 penalty.
Key dates for the 2025/26 tax return
| Date | What it means |
|---|---|
| 5 April 2026 | The 2025/26 tax year ended |
| 5 October 2026 | Deadline to register for Self Assessment if you're filing for the first time |
| 31 October 2026 | Paper return deadline |
| 30 December 2026 | File online by this date to have tax under £3,000 collected through your PAYE tax code (if eligible) |
| 31 January 2027 | Online return deadline, balancing payment for 2025/26 and first payment on account for 2026/27 |
| 31 July 2027 | Second payment on account for 2026/27 |
What to gather before you start
- Your Unique Taxpayer Reference (UTR) and Government Gateway login
- P60 or P45 from any employment, and P11D details of benefits
- Self-employment income and expense records for the year
- Rental income and property expenses, including mortgage interest
- Bank and building society interest, and dividend statements
- Details of any assets sold that could give rise to a capital gain
- Pension contributions and Gift Aid donations
- Any Child Benefit received, if your income is over the threshold
Why file early?
Filing early doesn't mean paying early — the payment deadline stays 31 January. But it gives you time to find missing paperwork, know exactly what you owe so you can budget, get any refund sooner, and avoid the January rush when HMRC phone lines and accountants are at their busiest.
What if you miss the deadline?
HMRC charges £100 as soon as the return is late, even if no tax is owed. After 3 months, daily penalties of £10 a day can apply for up to 90 days, followed by further penalties at 6 and 12 months. Interest and late payment penalties are charged on tax paid late. If you had a reasonable excuse, a penalty can sometimes be appealed.
Let us handle it
Send us your records and we'll prepare and file your return well ahead of the deadline, and tell you exactly what to pay. See our Self Assessment tax return service.
Frequently asked questions
When is the 2025/26 Self Assessment deadline?
31 January 2027 for online returns. Paper returns were due by 31 October 2026.
What happens if I miss the 31 January 2027 deadline?
An automatic £100 late filing penalty applies, with further penalties after 3, 6 and 12 months, plus interest on any tax paid late.
Do I have to pay my tax when I file?
No — you can file early and pay by 31 January 2027. Filing early simply tells you how much you'll owe.
Official guidance: HMRC: Self Assessment tax return deadlines
Reviewed November 2026. This guide is general information based on rules at the date shown and is not advice for your specific circumstances. Tax rules change — contact us before acting.