if applicable you'll get a supplemental schedule showing how to compute your gain.
there will be a column which you need to fill in for the sales price (the same as on the 1099-B
the next column should be your purchase price which you need to fill in ( should be the same as the cost on the 1099-B
the next column should be adjustment to basis
the next column which you need to compute is total gain or loss
= sales price - purchase price (unadjusted cost basis) - adjustment to basis (can be positive or negative
say 50,000 , 30000 , -20000
then 50000 -30000 - (-20000) = 50000 -30000+20000 =40000
proof your cost basis of 30000 was reduced to 10,000 by the negative adjustment to basis leaving a basis of 10,000
sold for 50.000 with basis of 10,000 so gain is 40,000
say 50000, 30000, 20000
then 50000-30000 -20000 =0
proof your cost basis of 30,000 was increased to 50,000 by the positive adjustment to basis giving you a basis of 50,000
sold with basis of 50,000 so gain is 0
however the or gain or loss may consist of two parts
if the next column says ordinary gain then that goes on form 4797 go into the disposition section and enter info for boxes/lines 1-4
on line 5 enter ordinary gain as sales price, line 7 basis of 0, line 9 same as line 5
for 1099-B purposes increase basis by amount on line 5
so if total gain was say 20,000 ordinary gain is 11000 capital gain would be 9000
