I have been participating in a ESPP with my employer, and I sold a chunk of my stock during this last year. The cost basis differs between the 1099-b and the 1099 supplemental form the broker sent me, and I am trying to determine whether to use the cost basis from the 1099-b or the 1099 supplemental for my tax filing this year.
What, specifically, are the key pieces of information I need to have to evaluate this question? Asked another way: what are the steps you (ideally, a tax professional) would take to find the right way to treat these documents?
