The online Self Assessment deadline for the 2025 to 2026 tax year is 11:59pm on 31 January 2027. Any tax you owe for that year is due on the same day. Miss it and HMRC charges an automatic £100 penalty, even if you owe no tax.
This checklist covers what sole traders and landlords need to gather, the key dates, and what happens if you file late.
Key dates for the 2025/26 tax year
| Deadline | What is due |
|---|---|
| 5 October 2026 | Register for Self Assessment if you are filing for the first time |
| 31 October 2026 | Paper tax returns |
| 30 December 2026 | Online return, if you want tax under £3,000 collected through your PAYE tax code |
| 31 January 2027 | Online return, balancing payment for 2025/26 and first payment on account for 2026/27 |
| 31 July 2027 | Second payment on account for 2026/27 |
Your Self Assessment checklist
For sole traders
- Your Unique Taxpayer Reference (UTR) and Government Gateway login
- Total sales or turnover for 6 April 2025 to 5 April 2026
- Business expenses: stock, software, phone and internet, travel, insurance, accountancy fees
- Bank statements for your business account, reconciled to your records
- Any equipment you bought (for capital allowances)
- Payments on account you already made
For landlords
- Rent received for each property
- Letting agent statements and fees
- Repairs, insurance, ground rent, service charges and other allowable costs
- Mortgage interest statements (relief is given as a 20% tax credit, not a deduction)
For everyone
- P60 or P45 from any employment
- Bank and savings interest, dividends and any foreign income
- Pension contributions and Gift Aid donations
- Student loan details, if you are repaying one
What if you file late?
HMRC’s late filing penalties are:
- 1 day late: £100
- 3 months late: £10 a day, up to £900
- 6 months late: 5% of the tax due or £300, whichever is greater
- 12 months late: another 5% or £300, whichever is greater
Paying late adds 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest. Penalties stack, so a late return and a late payment can cost far more than the tax itself.
Making Tax Digital is now live for some taxpayers
Since 6 April 2026, sole traders and landlords with qualifying income over £50,000 must keep digital records and send quarterly updates under Making Tax Digital for Income Tax. The threshold drops to £30,000 from April 2027. Read our guide: Making Tax Digital for Income Tax: who must comply and when.
How we help
Our UK team prepares and files Self Assessment tax returns for sole traders, landlords and company directors. We collect your records, claim every allowable expense and file well before 31 January. See all our UK accounting services.
Frequently asked questions
When is the Self Assessment deadline for 2025/26?
The online deadline is 11:59pm on 31 January 2027. Paper returns had to reach HMRC by 31 October 2026.
What is the penalty for missing the Self Assessment deadline?
An automatic £100 penalty, then £10 a day after 3 months (up to £900), and further penalties at 6 and 12 months.
Do I still need to file if I owe no tax?
Yes. If HMRC has asked you to file a return, you must file it by the deadline even if no tax is due, or you will still be charged the £100 penalty.
What are payments on account?
Advance payments towards your next tax bill, each normally half of the previous year’s bill, due on 31 January and 31 July.
Want us to handle it?
Talk to a UK accountant at Tax Expert. Fixed monthly fees, no surprise bills.
Sources: GOV.UK: Self Assessment deadlines · GOV.UK: Self Assessment penalties. This article is general information, not tax advice for your situation. Last reviewed October 2026.