The only thing you can know for sure about your 2018 return is that the IRS has it, since you used a mailing service that shows that to you.
You will not be notified that the refund is on its way. You have to watch your own account.
Sometimes using "zero" for the 2018 AGI will let it be e-filed and accepted. Since your 2018 return was filed late, the IRS does not have a 2018 AGI in the system for you---so zero can work.
No, you do not have to amend it later to enter the actual 2018 AGI--that is only used for e-filing.
If it still rejects using zero, then you have to print, sign and mail 2019.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
