The Self Assessment deadline for the 2025/26 tax year is 31 January 2027. If you are self-employed or a landlord, that date matters for three reasons. This guide gives you a plan for the next few weeks. It is general information, so check GOV.UK for current rules.
What is due on 31 January 2027
- Your online return for 6 April 2025 to 5 April 2026.
- Payment of any tax you owe for 2025/26.
- Your first payment on account towards 2026/27, if HMRC asks you to make them.
A paper return was due earlier, on 31 October 2026, so most people now file online. See our full Self Assessment guide and the deadlines checklist.
A plan for the next few weeks
- This week: find your Unique Taxpayer Reference and make sure you can sign in to your HMRC account.
- November: reconcile your bank for the whole tax year and check every invoice and expense is recorded.
- December: run your profit and loss for 6 April to 5 April and review your allowable expenses.
- Early January: complete and file the return. Filing early gives you time to arrange payment.
- Before 31 January: pay the bill and diary the next payment on account for 31 July.
What you will need
- Your income and expenses for the year (a profit and loss report).
- Records of any other income, such as employment, rental income or interest.
- Your bank details and your Government Gateway sign-in.
Penalties if you are late
- Filing late: an automatic £100 penalty, even if you owe nothing. After three months, daily penalties can add up to £900, and further penalties follow at six and twelve months.
- Paying late: interest on the unpaid tax, and additional penalties if it is still unpaid after 30 days, six months and twelve months.
If you cannot pay in full
File your return on time anyway, because the filing penalty is separate. Then contact HMRC as early as you can. Depending on how much you owe, you may be able to set up a payment plan online, spreading the bill over several months. Check GOV.UK for current eligibility and limits.
Tips for avoiding a January scramble
- Set aside a percentage of every payment for tax, so the bill is not a shock.
- Keep business and personal money separate.
- Reconcile your bank every month, not once a year.
- Use our self-employed tax calculator to estimate your bill.
Looking ahead: Making Tax Digital
If your qualifying income is over HMRC’s threshold, you will move to quarterly updates. Read about April 2027 changes.
How AvrioBooks helps
With invoices, bills and your bank in one place, the figures for your return are one report away. Export your profit and loss to PDF, Excel or CSV and use it to complete the return, or send it to your accountant.
Frequently asked questions
What is the Self Assessment deadline for 2025/26?
31 January 2027, for both filing online and paying the tax due.
What happens if I file late?
You receive an automatic £100 penalty, with further penalties the longer the return is outstanding.
What if I cannot pay my tax bill in full?
File on time, then contact HMRC as early as possible. You may be able to set up a payment plan. Check GOV.UK for eligibility.
Do I make a payment on account on 31 January 2027?
If your bill is above the threshold, your first payment on account for 2026/27 is due on 31 January 2027, with the second on 31 July 2027.
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