You can transfer your past year's Turbotax Desktop return into TurboTax Online. However, since TurboTax Desktop only saves your tax files onto your computer, you won't be able to view or adjust any returns you made in the Desktop version in Turbotax Online.

What is the cost for Turbo Tax for Mac?  Previous Windows version allowed 8 returns.  I need to complete 3 returns.  How will this work? 

@michel-leclair1 We don't have a version specifically for Macs. Instead we have TurboTax Do It Yourself (Online) which you can use on any computer that has a modern web browser.

If you pay per return, the cost is based on what you enter on your return. You can see the different versions and why they include here: https://turbotax.intuit.ca/tax/software/online

You can also go to a 3rd party retailer like Costco, Amazon, Staples, Walmart, etc... and buy multi-return packages. They set the prices, so you may find it cheaper at one place rather than another. The Deluxe package comes with 8 Deluxe returns, though you may need to pay extra if you have a return that has something not covered in Deluxe.

Note: Just like in TurboTax Desktop, if you prepare your return together with with a spouse/partner, that counts as 2 returns.