I keep seeing Turbotax people say that you need to mail the 1099-B but this is frankly incorrect and bad advice. You only need to mail the 1099-B if you enter sales summaries onto Schedule D with adjustments, which does not generate Form 8949 with the details. If you enter the sales items with adjustments at the detailed level those will generate Form 8949 and go onto Schedule D (line 1b, 8b etc), enter the rest as sales summaries and those go onto Schedule D on line 1a, 8a. TT should provide a message saying you don't need to mail anything. If you use desktop version in Forms mode you can confirm that also on the 1099-B worksheets, there is a checkbox at the very bottom indicating if anything needs to be mailed.
I'm not a CPA/Experrt but I've done this for many years and never mailed anything, and I do not import 1099s it's not worth the hassle especially if there are problems. Give it a try for a few entries to see the process, you don't have much to lose.
