Once registered as self employed, HMRC will write to you in April/May to request completion of your SA100 Self Assessment Tax Return.
However, if you don’t receive a letter, you’ll need to still complete a return.
Use our quick check to view your deadlines
What is a Tax Year?
‘Tax Years’ traditionally run from April – March the following year.
The table below shows recent tax years, and the deadlines for online submission and payment of your taxes.
| Tax Year | Start Date | End Date | Deadline Date* |
|---|---|---|---|
| 2023/24 | 6 April 2023 | 5 April 2024 | 31 January 2025 |
| 2024/25 | 6 April 2024 | 5 April 2025 or 31 March 2025** | 31 January 2026 |
| 2025/26 | 1 April 2025 | 31 March 2026 | 31 January 2027 |
| 2026/27 | 1 April 2026 | 31 March 2027 | 31 January 2028 |
*The deadline date is when you must pay all tax which is due, including any national insurance contributions and the first Payment on Account (if applicable).
** 2024/25 was a transitional year for Basis Period Reform to prepare for Making Tax Digital. We moved our packages to follow the HMRC Calendar year to make quarterly processes easier (and to avoid remembering a random date in April!)
Example
Claire began her self employment on 23 July 2025
This falls within the 2025/26 financial year (1 April 2025 – 31 March 2026)
She must complete her tax return and pay any tax, national insurance and her first payment on account (if applicable) by 31 January 2027.