I use Sched D. I can tell you that I trade about 1500 trades per year. I do not write off my expenses on a schedule C. I write them off on my Schd A which only allows you to write them off if you exceed 2% of your income. Using a Scd C would allow one to write them all off, but I think there is a fine line regarding the use of a Schd C for purposes of trading. My expenses are not that huge that I would want to take that chance. There is also mark-to-market where you report all your trades regardless of whether or not you sold them at the end of the year.