This answer was for the 2016 website. See the 2017 info in the next comment.
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Yes. You can come and go. Online TurboTax saves your data each time you change screens. To exit, click at the top on MY ACCOUNT, then choose "Save and Sign Out." Occasionally for some people, that Sign Out link will be temporarily frozen. In that case, then just go to a neutral screen where you weren't inputting any data and close the browser window.
When you return, log into your account and go to the 2016 Tax Timeline. Click the orange button "Take me to my return."
This answer was for the 2016 website. See the 2017 info in the next comment.
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Yes. You can come and go. Online TurboTax saves your data each time you change screens. To exit, click at the top on MY ACCOUNT, then choose "Save and Sign Out." Occasionally for some people, that Sign Out link will be temporarily frozen. In that case, then just go to a neutral screen where you weren't inputting any data and close the browser window.
When you return, log into your account and go to the 2016 Tax Timeline. Click the orange button "Take me to my return."
NOTE: The answer above was for the 2016 website. Here is updated info for 2017.
The website has a new look for 2017. If you are working on your return, you can sign out by going to the left column menu and scroll way down to the bottom, where there is a "Sign Out" link. If you scroll the whole screen down, that may not be enough to see it.. You can scroll the left column menu separately from the main part of the screen.