Self Assessment Deadlines for 2025–26: Key Dates Explained for Sole Traders

If you are a sole trader in the UK, Self Assessment is how HM Revenue and Customs (HMRC) collects Income Tax on your business profits and any other untaxed income. The 2025–26 tax year runs from 6 April 2025 to 5 April 2026, and it’s important to understand the key deadlines to avoid penalties.

Registering for Self Assessment

If you have not sent a tax return before, or you registered previously but did not need to send one for 2024–25, you must tell HMRC by 5 October 2026 that you need to complete a return for the 2025–26 year. This is done by registering for Self Assessment. If you miss this deadline, HMRC will send you a letter or email with a different deadline, usually three months from the date of that communication. However, you must still pay any tax owed by 31 January 2027 to avoid penalties.

Filing Your Tax Return

Paper return deadline: If you choose to send a paper tax return, HMRC must receive it by 31 October 2026 at 11:59pm. You can send it any time from 6 April 2026 onwards.
Online return deadline: You must file online by 31 January 2027 at 11:59pm. Online filing is the most common method and allows you more time than paper returns.
Early submission: You can submit your return any time after the tax year ends on 5 April 2026, so from 6 April 2026 onwards.

Note that if you want your tax bill to be collected through your tax code, you must submit your return by 30 December 2026. Missing this date means you will need to pay your tax bill by other means.

Paying Your Tax

Any tax you owe for 2025–26 must be paid by 31 January 2027 at 11:59pm to avoid penalties. This includes the balancing payment for the year and the first “payment on account” (an advance payment towards the next year’s tax). A second payment on account, if applicable, is due by 31 July 2027.

If you do not know your exact profit for the whole tax year when filing, you still need to send the return by the deadline. You can estimate your figures and adjust them later if necessary.

Summary of Key Dates for Sole Traders

5 October 2026: Deadline to tell HMRC you need to send a return for 2025–26 if you are new to Self Assessment or previously registered but not required to file for 2024–25.
31 October 2026: Deadline for HMRC to receive paper tax returns.
30 December 2026: Deadline to file online if you want to pay your tax through your tax code.
31 January 2027: Deadline to file online tax returns and pay any tax owed.
31 July 2027: Deadline for second payment on account, if applicable.

Keeping accurate records of your income and expenses throughout the year will help you complete your return correctly. If you miss deadlines, penalties and interest may apply, so it’s best to plan ahead and submit your return and payments on time.

Official reference: https://www.gov.uk/self-assessment-tax-returns. Topic-specific official guidance. Always check the latest official guidance. Related forms: Browse our form category.

Important: This article provides general information. Government rules, forms and procedures can change, and this article may not reflect the latest updates. Check current GOV.UK guidance or the relevant authority before relying on it. ITG & Co. is independent and is not affiliated with a government department.