Do I need to file for an extension if I have to wait for Tax Transcripts by mail (to verify my AGI from 2017) that won't be received until after the 15th?

[kj_529]

I got a IND-031-04 error response when I attempted to e-file.
I do not have any qualifying accounts that will let me get my Tax Transcripts electronically either.

[BMcCalpin]

In the worst case, file your extension on paper. After all, it's the day that you mail it that matters, not the date the IRS receives it.

If you can't file the extension through TurboTax, try using the IRS - Free File and Free File Fillable Forms, both available at IRS.gov, which allow you to prepare and e-file Form 4868 for free. (if you do this, make a copy of your 4868 because you may need to enter some of the data into your TurboTax return when you get back).

However, you will need to provide certain information from your 2017 tax return. If you don't have that information and can't get it before April 15th, then print, complete, and mail the 4868. What counts is the day that you mail it, not the day the IRS receives it. You can find the form at https://www.irs.gov/pub/irs-pdf/f4868.pdf