I'm pretty sure that you didn't "import"; is every single trade you made during the year on that Form 8949 that's part of your income tax return? If not then you didn't import, you told TurboTax that you'd enter "summarized" trade information.
You must report each and every sale to the IRS. You do this by filing
out Form 8949. That information comes right off your 1099-B and if you
enter sales "one at a time" each sale is listed there for you. But if
you "summarize" then you must submit either a Form 8949 or a schedule of
some sort with the same information on it to the IRS. The Form 8453 is
the "transmittal" form used to send in the Form 8949 or substitute.
(You probably can send in a copy of your 1099-B if each trade is listed
there with the same information that would show up on a Form 8949.)
Tom Young
