I thought by their question they wanted their 2018 AGI. If they need their 2017 AGI to e-file their 2018 return, then
You can find your 2017 AGI: In TurboTax Online or the mobile app under Your tax returns & documents. On your originally-filed 2017 tax return, form 1040 (Line 37), 1040A (Line 21), 1040EZ (Line 4), 1040NR (Line 36), Form 1040X (Line 1, column A)
