After you file
Starting in 2023, they moved the "Amend a Return" button way down in the bottom left corner, and it may be out of view. Like you, I at first didn't see it. I had to scroll way down the screen to make it appear. See image below.
NOTE: Do not make any changes in your return until the Amend process instructs you to do so. Also, it's a good idea to first make a backup of the original *.taxYYYY data file and PDF before amending, and archive them somewhere safe and secure. Then, if something goes haywire during the amending process, you still have the original data file and PDF. Be sure it has a different file name, such as "2023taxreturn_original" (or whatever you choose), so it doesn't get mixed up with the amended return's data file.
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