I can only guess that you are using the RSU step be step process and entering something incorrectly. I generally advise against using that method as 1) it's not necessary from an "income tax reporting" standpoint, unless the income from the vesting never showed up on your W-2, and 2) people commonly get confused in this interview and make mistakes.
So, if really know your correct basis per share - not what the broker is reporting on the 1099-B which probably is $0 - delete that trade and start over. (Just to make sure that you do know your basis per share, if 20 shares vested and the employer used $10 per share as the "fair market value", then $200 showed up on the W-2 as compensation arising from the vesting. And $200/20=$10 per share.)
Using the default TurboTax 1099-B entry form enter the 1099-B as it reads then click on the "I'll enter additional info on my own " blue button. On the next page enter the correct basis in the "Corrected cost basis" box. The correct basis is (number of shares sold) x ($10)
TurboTax will report the sale on Form 8949 "as reported by the broker" but will put an adjustment figure into column (g) of the Form, a code "B" into column (f) of the Form, and the correct amount of gain or loss which includes the adjustment.
Tom Young
(The RSU step by step interview will get you to the right answer if you enter the correct information.)
NOTE: TURBOTAX CHANGES THE SECURITY SALES INTERVIEW JUST ABOUT EVERY SINGLE YEAR. THE INSTRUCTIONS ON "HOW TO FIX" THE BASIS REFLECT THE STATE OF THE INTERVIEW FOR TAX YEARS 2016 AND 2017
