The easiest way to access your AGI information is by logging
in with the email you used last year (2015).
If you don't remember the email address/account information
associated with your 2015 account, you can use the account recovery tool to access this information- https://myturbotax.intuit.com/account-recovery/.
You can also access your AGI by contacting the IRS directly at 1-800-829-1040.
[Edited 1/23/17]
https://ttlc.intuit.com/replies/3301618