Your question might very well have left out important information.
If there's a missing prefatory statement along the lines of "I summarized all my security trades" - meaning you didn't enter each and every sale into TurboTax but only entered summary proceeds and cost figures for all your trades - then you do need to send in to the IRS a substitute Form 8949, (the 1099-B provided by the broker will probably suffice), accompanied by IRS Form 8453. You do have to fill out some information on that form, but it doesn't need to be signed.
