If you had to get an IRS transcript to get your AGI from last year to e-file, you can get back to this section in TurboTax by going back through the File section. You will need to go through the questions and you will be prompted for your AGI during the interview process.
You can find your
last year's AGI on your 1040 form here:
Form 1040 – Line 37
Form 1040A – Line 21
Form 1040EZ – Line 4
Form 1040NR – Line
36