If you bought the (USA) 2017 TurboTax Download (not online) software, you may do an unlimited number of tax returns. No additional purchase is required. They have to be printed and mailed. You can no longer e-file a 2017 tax return.
2017 online software is no longer available, at all.
To purchase 2017 (or earlier) download (desktop) software, see
https://turbotax.intuit.com/personal-taxes/past-years-products/
