Re -- Attaching PDFs to e-filed returns:
I asked a question about that recently, and it was suggested I research prior answers. Here's the most complete I've found, and it's updated as of 1 April 2020:
TurboTax Help Intuit
posted May 24, 2019 4:10 PM; last updated April 01, 2020 3:46 AM
"When a tax return can't be e-filed no matter what you do"
Although millions of tax returns are successfully e-filed every year, some returns simply can't be e-filed or keep getting rejected even though there's really nothing wrong with them.
Returns cannot be e-filed if they:
Many nonresident and part-year state returns cannot be e-filed either, due to circumstances beyond our control (we'll let you know if your non- or part-year resident return must be paper-filed).
In addition, certain returns keep getting rejected because somebody already claimed a dependent on the return or because of incorrect information in the IRS database. In these cases, there's really nothing you can do to "fix" your return so you can e-file it. For this year at least, you'll need to file a paper return instead.
