How can I make a correction to a self assessment return?

I submitted my return over the weekend and realised almost immediately that I had omitted a source of income. How can I correct this?

Hi,

You can go back in to amend it.

1. Sign in using your Government Gateway user ID and password. 
2. From ‘Your tax account’, choose ’Self Assessment account’. 
3. Choose ‘More Self Assessment details’.
4. Choose ‘At a glance’ from the left-hand menu. 
5. Choose ‘Tax return options’. 
6. Choose the tax year for the return you want to amend. 
7. Go into the tax return, make the corrections and file it again.

Thank you.