I've received a letter from HMRC stating that I've submitted an amended return but no original has been received – what do I do?

An online amendment would've been sent to HMRC if the Amended box was ticked in the online filing settings page when you filled in your original return.

If you haven't submitted the original return yet, follow these steps:

1. Click on Check and Finish.
2. Click on File online.
3. Click on Re-submit and then untick Amended.
4. Click on File Online/Submit.