If that other place made an error, they should be willing to make it right. But to amend 2020 using TT, you must wait until your original filing has been fully processed, in case the IRS changes anything. Then:
(1) Recreate your exact original return (or as changed by the IRS) in TT Online.
(2) Tell the system you will file by mail, but then do not actually do so.
(3) Amend.
Depending upon the complexity of your return (and your reason for amending), you may be able to use TT Free.
