My efile keeps getting rejected because it keeps saying my AGI from last year is wrong. I have never filed a tax return. I just turned 18 in 2018?

[xmasbaby0]

Use zero for your 2017 AGI.  If zero does not work then you will not be able to e-file.  Then you can just print, sign and mail your tax return instead of e-filing it.

When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s.  Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS received the return.