if this is a 1099-B the box checked for should be B, C, E, F or X
8949 instructions
You received a Form 1099-B (or substitute statement) and the basis shown in box 1e is incorrect
• If this transaction is reported on a Part I with box B checked at the top or if this transaction is reported on a Part II with box E checked at the top, enter the correct basis in column (e), and enter -0- in column (g).
also enter code B in column (f)
what do I do if the items are BOX B OR E- enter basis in column e and skip columns f and g. do at your own risk.
there are no specific instructions for what to do if BOX C, F OR X are checked.