If you input 1099B at summary level but there are adjustments to the cost basis (e.g. AMD, Wash Sale) or noncovered sales, this will trigger the need to send the details to IRS either on 8949 or "statement with the same information" using Form 8453. If you are on TT Desktop, at the bottom of the Capital Asset Sales worksheet there is a line which shows whether the mail-in statement is required.
What to do, depends how many adjustments you have.
One way to avoid this mailing is to split up the 1099B and enter any sales which have adjustments at the detailed level, and the balance of the 1099B can be input at summary level. If you don't have many it doesn't take long to do. (This is what I do - importing 1099s is not worthwhile).
If you have a high volume of adjustments and import is not an option, you can always mail in Form 8453 with the pages from the 1099B which have the adjustment details (not a CPA but don't think the whole thing is needed; and I suspect you'll never hear about it again - they probably just shred it below a certain threshold).
I think TT Online has more options to import from PDF, or upload the PDF for this reporting requirement, but not tried it.
