If you downloaded the tax data file from the online edition, the data file can only be opened by the TurboTax software for the same tax year as the tax data file. The tax data file will have a file extension of .taxyyyy where yyyy is the tax year, eg .tax2018 for tax year 2018.
If you download the PDF of the online tax return that file can be opened by any compatible PDF viewer, such as Adobe Reader.
To access your current or prior year online tax returns sign onto the TurboTax website with the userID 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)
