After you file

The 2018 AGI is on the 2018 Federal tax return you filed Form 1040 Line 7

Or go to this IRS website for free federal tax return transcripts - https://www.irs.gov/individuals/get-transcript

 

If your tax return continues to be rejected with the 2018 AGI then enter a 0 (zero) for the AGI and e-file again.

If this is also rejected then you will have to print and mail the tax return.

See this TurboTax support FAQ for printing a tax return for mailing - https://ttlc.intuit.com/community/printing/help/how-do-i-print-and-mail-my-return-in-turbotax-online...