Use the AGI from the first original return.
You need your 2018 AGI to efile 2019. The AGI is on 2018 1040 line 7.https://ttlc.intuit.com/community/agi/help/how-do-i-find-last-year-s-agi/01/25947 Or see the screen shot by critter on this one,https://ttlc.intuit.com/community/taxes/discussion/re-i-m-order-to-complete-my-taxes-it-is-asking-me...
