Which tax year are these deadlines for?
This calendar covers income earned from 6 April 2025 to 5 April 2026. A return due in January 2027 normally reports that earlier year, not income earned throughout calendar year 2026. HMRC can set a different filing deadline if it issues your notice to file late; check the notice.
Your 2025 to 2026 Self Assessment calendar
- 5 October 2026: usual deadline to tell HMRC if you need a return and have not filed before, or need to register again.
- 31 October 2026: deadline for HMRC to receive a paper return.
- 30 December 2026: online filing deadline if you want eligible tax collected through your PAYE tax code. Conditions apply.
- 31 January 2027: usual online filing deadline and balancing payment for 2025 to 2026.
- 31 January 2027: first payment on account for 2026 to 2027, if required.
- 31 July 2027: second payment on account for 2026 to 2027, if required.
Why your January bill can be more than you expect
Payments on account are advance payments towards the next tax year, usually half of the previous year's relevant bill each. They normally apply unless that bill is less than £1,000, or more than 80% of your tax was paid outside Self Assessment, for example through PAYE. Check your HMRC calculation rather than assuming everyone pays them.
Illustration: if a first-time filer owes £2,000 for 2025 to 2026 and payments on account apply, January 2027 could require £2,000 plus a £1,000 first payment on account. A second £1,000 would be due in July 2027. This is an example, not a calculation of your own liability.
Missed the registration date? Act now
Do not wait until January. Use HMRC's service to check whether you need a return, register or reactivate your account where necessary, and arrange access to online filing. HMRC says that if you register after 5 October, it will give you three months from its letter or email to file. This does not change the 31 January 2027 payment deadline. Follow the dates in your notice and contact HMRC or your accountant if you cannot meet them.
MTD updates are a separate calendar
For people required to use MTD for Income Tax in 2026 to 2027, standard quarterly updates are due on 7 August 2026, 7 November 2026, 7 February 2027 and 7 May 2027. The annual tax return for that tax year is due by 31 January 2028. Joining MTD does not remove annual filing or turn every quarterly update into a tax payment.
Your January 2027 return for 2025 to 2026 and your 2026 to 2027 MTD updates can therefore overlap. Keep the tax year and the type of submission clear.
A practical checklist before filing
- Reconcile invoices and customer payments with your records and bank statements.
- Gather expense receipts, CIS deduction statements and other income information where relevant.
- Check your accounting method, business-use proportions and any adjustments with your accountant.
- Confirm submission was accepted and allow time for the payment method you choose.
Fixxa helps organise income, expenses and invoices. It does not currently submit Self Assessment returns or MTD updates to HMRC; direct HMRC submission is coming soon. You still need the appropriate HMRC service, compatible software or an agent.