If you entered 2019 tax data on the TurboTax online 2020 tax return, clear the return. Nothing can be transferred to a 2019 tax return from a 2020 tax return.
If you have not paid for the online edition you are using, have not filed your tax return or registered the Free edition, then you can clear your return and start over. Click on Tax Tools on the left side of the program screen while working on the 2020 online tax return. Click on Clear & Start Over.
To complete and file a 2019 tax return using TurboTax you would need to purchase, download and install on a personal computer one of the 2019 desktop editions from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/
A 2019 tax return can only be printed and mailed, it cannot be e-filed.
