If you have income that isn’t taxed through PAYE, you have to register for Self Assessment. However, this is only if you haven’t registered before. If you’ve already registered before, you don’t need to register again.
You have to register by 5 October, after the tax year has ended. For example, for the tax year that ends on 5 April 2026, you would have to register by 5 October 2026.
If you’re not registered, HMRC won’t send you a tax return or notify you to complete one.
How to register
You can register online on the HMRC registration page.
To complete the registration, you’ll need a Government Gateway User ID and password. HMRC sends these by post, so the process can take time.
Alternatively, you can register by post using form CWF1.