Self Assessment is a system HM Revenue and Customs (HMRC) uses to collect Income Tax.
Tax is usually deducted automatically from wages, pensions and savings. People and businesses with other income must report it in a tax return.
If you need to send one, you fill it in after the end of the tax year (5 April) it applies to.
This guide is also available in Welsh (Cymraeg).
Sending your return
Send your tax return by the deadline (31 January if you file online).
If you didn’t send an online return last year, allow extra time (up to 20 working days) as you’ll need to register first. There are different ways to register if you’re:
Filling in your return
You need to keep records (for example bank statements or receipts) so you can fill in your tax return correctly.
You can get help filling in your return.
Paying your bill
HMRC will calculate what you owe based on what you report.
Pay your Self Assessment bill by 31 January (or 30 December if you want HMRC to collect tax automatically from your wages or pension).