say you open a position 12/31/02 and you exit 1/1/03. this trade would go on 2003's tax return because it was closed in 2003, correct? thanks
Yes, but remember that wash sale rules will still apply to that open trade. This is the case for any trades you hold into the new year.
If you've elected to use the mark-to-market accounting method, it's as if a fictional sale takes place on the last day of your tax year. Your gain or loss is the difference between the your basis and the fair market value of your security on that day.
Are options required to be mark to market? My accountant takes care of this so I don't know, but on one of my returns, that was not mark to market accounting, one year there were open option positions that I had to mark to market even though I didn't on the open stock positions.