Do I really need to mail hard copy of 8453, 8949, and 1099-Bs? The forms show in the filing preview (so are e-filed, right?) and IRS was already sent the 1099-Bs, right?

[tt2627jst-]

Al 1099-Bs show a cost/basis, but 8949 Part II has checked Box (E) "Long-term transactions reported on Form(s) 1099-B showing basis WASN'T reported to the IRS" - but basis WAS reported.

[JohnW15]

Right -- the IRS receives the same 1099-Bs that have been issued to you.  This is just an IRS requirement when you file electronically.

Please see TurboTax Anthony's explanation below.

https://ttlc.intuit.com/replies/6047751