Yes, you can still file, but you would have to print and mail. You can't e-file without your 2017 AGI.
Here is where to find it:
Form 1040 – Line 37
Form 1040EZ – Line 4
Form 1040NR – Line 36
Form 1040X – Line 1, Column A
If you prepared in TurboTax
Online, here is how to access your prior return:
1.
Make sure you’re signed in to
your TurboTax account.
2.
Select Tax Home from
the left menu.
3.
Scroll down to Your tax
returns & documents and select 2017.
4.
Select View adjusted
gross Income (AGI)
If you prepared your tax return in TurboTax CD/Download, it should be saved on your computer.
If you prepared your tax return through other software, you can
request a transcript from the IRS.
Follow this link: Get
a Transcript
If you filed your tax return after October, 2018, use $0.
For more information, including a picture reference, follow this
link: How
to Find Last Year's AGI