The 2020 TurboTax software is used to amend a 2020 tax return.
See this TurboTax support FAQ for amending a 2020 tax return originally completed and filed using TurboTax - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-2020-return/L3XdA1Pw8_U...
