If a missing Form 1099-B is not the reason that the IRS thinks your tax return needs Schedule D, it's possible for the IRS to think that your tax return should have included Schedule D if you had dividends or capital gains reported only on Form 1099-DIV, you mailed your tax return and the IRS data transcriber failed to transcribe the mark in the checkbox on Schedule 1 line 13. (It happened to me once.) The resulting entry in your tax-return transcript on line 13 without the corresponding checkbox mark implies to the IRS that your tax return should have included Schedule D when, in fact, it was not required. If this is the only reason that the IRS thinks you need to provide Schedule D, rather than trying to convince the IRS that no Schedule D was required you can simply open your tax file using the CD/download version of TurboTax, switch to forms mode, open Schedule D, print the form and mail it to the IRS.
If you e-filed the tax return, disregard this possibility.
