Do I need to declare income that has already been taxed?

Hi folks, I worked as a supply teacher for an agency last year and got taxed on that income before it reached my account. Do I need to declare this as self-employment income? If so, any more details on how and where I need to do this? Many thanks, Lila

Hi,
No this is employment income and if you are completing a tax return, this income should already be there. If not, you still need to include it as it is part of your worldwide income.
Thank you.