Notification of foreign income

Good morning my question is if I have only completed one self assessment for 2023/2024 and I have realised I undeclared foreign income from a previous year can I go back and input the undeclared foreign income or would that only be possible if I had completed a self assessment for the previous year. Thanks.

Hi CBX500,
For previous years, you can only amend the 22/23 tax return online, if you sent one. other years whether you filed a return or not would need to be a letter and send it to:
HMRC PAYE & Self Assessment
BX9 1AS.
Thank you.