Thanks for your reply. I have already amended the 2020 return using the TurboTax 2020 software installed on my laptop. The issue is that the Form 1040-X generated by TurboTax 2020 is "(Rev. January 2020)" and the IRS Form 1040-X Instructions state that the July 2021 revision needs to be used for amending returns for 2019 and later.
