You do not need to purchase TurboTax 2021 again. You use the same one you purchased in the first place to do your 2021 taxes. The software will likely tell you it needs updates and you can go ahead and update it. Then when you go to file open return, before you select last year's return file, select "amend a filed return" and then follow the prompts. This will allow you to select the previously filed return and then make your updates.
However, you may not be able to file your amended return electronically even though you did last year and it was accepted. I am having this same issue and the problem is TurboTax won't let you proceed with filing electronically if the signed date of amended return is past 12/31/2023. If anyone knows a solution to avoid having to print and mail an amended return, I would sure like to know. Apparently, the TurboTax team has not had time to implement some critical changes.
