1040X Amended Return

How is it affecting 2018?  Do you need the AGI to efile 2018?  Use the AGI from the original 2017 return not the amended one. 

By the way, you didn't need to wait to file 2018.  

If you used the desktop version of TTX 2017 to file your return and/or to amend your 2017 return, and you used the desktop version of TTX 2018 to complete your 2018 return, the only possible way to "update" the stuff imported from the 2017 return is to delete the .tax2018 file in the documents/turbotax directory and start over from scratch. That's the only way possible to import the corrected data from your 2017 tax file.

If you are attempting to e-file your 2018 return and the program is asking for your 2017 AGI, try three numbres.

First, use the AGI off line 37 of your *ORIGINALLY* filed form 1040 or line 4 of the 1040-EZ. That same amount is also on the 1040-X line 1, column A.

If that doesn't work then use the AGI on the 1040-X line 1 column C.

If that doesn't work then when asked for the AGI, enter a zero.

If tha doesn't work, then  you have no other choice but to print, sign and mail it to the IRS.

I realized my 2017 income was incorrect when I was filing my 2018 taxes

So after amending your 2017 return you need to start over with your 2018 return from scratch, in order to import the updated information from the 2017 return into the 2018 return.

Now if the absolute only thing you did when you amended your 2017 return was add another W-2, with *rare* exception that changes nothing for your 2018 return. So there's no need to start the 2018 return over and import the data again.

However, when you e-file the 2018 return you may need to use the AGI from your 2017 return from BEFORE you amended it.