I know this is an old post but I am in the same boat. From what I understood, you sold qualifying ESPPs at a loss (I did too LOL), your cost basis should be the same price you paid (The 85% price). If you did disqualifying ESPPs, then you have to use the 'adjusted cost basis'. Do you use e-Trade? If so, they provide a supplemental doc each year that has an adjusted cost basis column. Use that doc.
