The IRS requires (if you e-file) the AGI information be provided to protect your identity unless they have issued a self-select PIN previously then you can use that. Please see this IRS link: https://www.irs.gov/e-file-providers/definition-of-adjusted-gross-income. You can mail your tax return to the IRS if you do not want to provide the AGI.
You can obtain your 2018 AGI from last year's return that you filed with TurboTax. Please make sure you login to TurboTax Online with the exact same User ID and password you used last year.
1. Sign In to TurboTax in the correct account from last year.
2. Go to the prior year section in My Tax Timeline.
3. Click View adjusted gross income .
Also, you can request a tax transcript online from the IRS.
Please see this TurboTax FAQ for more Information: https://ttlc.intuit.com/community/agi/help/how-do-i-find-last-year-s-agi/00/25947