Steps to amend 2021 return if client already E-Filed.

Input their return as original, Select original return was successfully E-Filed and E-File that return.

Taxing Authority will reject as duplicate of previously accepted transmission.

Go into return and select File amended electronically, go to 1040X and select 2021 tax year.

Make appropriate changes in return to accurately file 1040X.

File Amended return.

This was totally different than filing a 2020 return but it seems to have worked.