You cannot prepare a 2017 return with TurboTax online. Online TurboTax can only prepare a 2019 return at this point in time. For a 2017 return, if you want to use TurboTax, you'll need to use 2017 desktop software (CD/download) on a computer. And it cannot be efiled; it has to be printed, signed, dated, and mailed. I'll also tell you at the end of this posting how to get 2017 forms from the IRS to prepare it manually, if you prefer.
You can purchase 2017 desktop software as a download at this page and install it on your computer:
https://turbotax.intuit.com/personal-taxes/past-years-products/2017
Minimum system requirements for Windows version:
https://ttlc.intuit.com/questions/1901571-minimum-system-requirements-for-turbotax-windows-software
Minimum system requirements for Mac version:
https://ttlc.intuit.com/questions/1899173-minimum-system-requirements-for-turbotax-mac-software
The 2017 return cannot be efiled. It will need to be printed, signed, dated, and mailed. It is recommended to mail by a method that has tracking such as certified return receipt, priority mail, etc.
If you have both Federal and state returns, you need to mail each one separately to its respective tax agency.
If you are due a Federal refund, it takes about 6 weeks for the IRS to process a mailed return.
OR another option if you have a simple return is to download the 2017 forms and instructions for free from the IRS website and fill them out manually.
https://www.irs.gov/forms-pubs/prior-year
