I don't have a loss, I have a gain. Fair market value was lower than cost basis because this was a short position. In other words I sold one contract at the higher price. At the end of the year, the contract had come down in value to the lower price. Because this was a short (bearish) bet, I made a gain as noted.
According to the instructions for form 6781, part III is not stated as optional. So I'm unclear why you believe it is. I don't think the fact that it's marked as Memo Only makes it optional. I also don't think that the fact that it's not part of the calculation necessarily makes it optional either. Do you have reference you can point me to showing that it's optional?
