If you did not save a copy of the original tax return before you started to amend the tax return the the original Form 1040 is no longer available in the TurboTax program. Only the amended tax return, Form 1040-X, and the changed Form 1040 are available.
Or go to this IRS website for free federal tax return transcripts - https://www.irs.gov/individuals/get-transcript
For a fee of $43 you can get a complete federal tax return from the IRS by completing Form 4506 - http://www.irs.gov/pub/irs-pdf/f4506.pdf
If you have not started to amend the return then download the PDF of the original tax return.
To access your current or prior year online tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/
Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show. Click on the Year and Click on Download/print return (PDF)
Or -
When you sign onto your online account and land on the Tax Home web page, scroll down and click on Add a state.
This will take you back to the 2020 online tax return.
Click on Tax Tools on the left side of the online program screen. Then click on Print Center. Then click on Print, save or preview this year's return. Choose the option Include government and TurboTax worksheets
