Can I still file electronically with Turbotax if I have a manually generated IRS form that Turbotax does not prepare

To attach Form 8990 to your tax return, you'll need to print and mail it.  Here's more info on Unsupported Forms and Calculations.

 

Make sure you really need to file Form 8990.  Here's Instructions for Form 8990.

 

You could also Efile now, and Amend later to add Form 8990 to your mailed amendment. 

 

@douglassbennett