Yes, you can file both a 2017 and 2018 tax return now, but you have to use different programs.
The TurboTax online editons are only for tax year 2018 and the 2018 tax return can be e-filed at any time up through October 15, 2019.
To complete a 2017 tax return using TurboTax you will need to purchase, download and install on a personal computer one of the 2017 desktop editions from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/
A 2017 tax return can only be printed and mailed, it cannot be e-filed.
