It is not whether you e-filed last year--it whether you filed a tax return last year--even if you mailed it. If you have a 2018 return look on line 7 for the AGI. That is how the IRS verifies your identity to allow you to e-file 2019.
Your 2018 tax return shows your 2018 Adjusted Gross Income (AGI) If you filed a joint return then the AGI is the same for each of you.
Form 1040 line 7
If you are using the same TT account that you used last year, you should also be able to find this number in your Tax Home for 2018
If entering the amount from your 2018 tax return does not work, then try entering “0” instead. If that does not work and you still cannot e-file, then print, sign, and mail your tax return.
You can get a free transcript of your past return from the IRS:
Note: If you filed late or amended your return, your correct 2018 AGI may not be in the system.
Note: If you mail your federal return, you will also need to mail your state return. You will not be able to e-file your state return.
Did you file a Joint return last year? There is only one AGI on a Joint return. You enter the same AGI for each of you. When did you file 2018? If it was later in the year like after September you might have to enter 0 for the AGI since it won't be in the IRS database to verify.
IMPORTANT: If you filed 2019 by mail, you filed it late with extension OR the IRS has still not processed your return, then you need to enter your AGI as "0". IRS is backlogged eons for 2019 taxes and even people who filed on time may not have their taxes "processed" from 2019, THUS regardless of your AGI you have listed on your taxes, the IRS still sees the AGI for verification as "0"
My 2020 taxes were "rejected" for this very reason, not knowing that because they had still not processed my 2019 taxes, that I needed to enter "0" for AGI for 2020. I went back after learning this VERY IMPORTANT tip and corrected and refiled and was ACCEPTED.
*Make sure you verify with TurboTax or your account professional. This is not legal advice.
This is gonna impact millions of others who do not know this info. Hope it helps.