Sunday 5 October 2025 is the deadline to notify HMRC of a new source of income or gain for 2024/25 where there is a requirement to register for and file self-assessment returns.
Those required to register for self-assessment includes anyone who:
- is self-employed or a sole trader in a business which commenced in 2024/25,
- is not self-employed but who had a new source of income or a gain in 2024/25, or
- became a partner in a partnership or any new partnership which commenced in business in 2024/25.
Failure to register by the deadline can result in HMRC charging a failure to notify penalty.