Did you use Online TurboTax in 2015, but don't find a 2015 return in
your 2015 Tax Timeline? If so, then you likely have multiple accounts
and signed into the wrong one. If you used the desktop version for 2015
(CD/download), then it won't be in an online Tax Timeline.
To get a list of your User IDs and recover account access, you can use the tool at the link below. Try using your phone number first.
NOTE: Before running the account recovery tool below, log out of all Intuit accounts including this user forum, or you might end up in a loop. Then clear your browser Internet cache, close your browser, then reopen it, and go to the link below. You may wish to copy this link so you can paste it into the new browser session.
If still no luck after running that on your phone number, User ID, or email address, then run the tool yet again, but this time choose the small blue link that says "Try something else", and it will look you up by SSN and other parameters.
Once you find the 2015 return, if it was prepared in Free Edition, the access will probably be locked until you pay for a 2016 product. We can tell you how to do that.
However, even if locked, there might be a link in the 2015 Tax Timeline under "Some things you can do" that says "View adjusted gross income (AGI)"
Or you may be able to download a free 2015 tax return transcript at this IRS website. .