Sadly, there's no easy way to do it without starting over on your return even if you've already entered all the info on all forms. Plus, it's tricky getting to the page on TT where you can actually select the Premier product. Using any of the links TT sent me in email, I end up at the free file product and can't escape that. Instead, I have to go to the TT main page as a new customer and select the Premier product. Then I can sign-in there and proceed with a blank slate. TT does have all my info from previous years, so prior years' information and carryovers are intact.
