If you filed with someone else last year, they should have given you a form, I believe it’s a 1040. It should have your AGI on it. If you filed with TurboTax, it should just save it for you.
Somehow, I have 2 logins with TurboTax and I started with this login last year, but finished with my other login. I had to log into last year’s account to get my AGI.
