I just did my taxes and I tally mine daily. Then I add my winning days together and my losing days together and keep 2 totals at year end. In the US, you can only claim as much losses as you have winnings (unless you claim expenses as a pro) AND you must state both your winnings and losses separately. NOT just the end result.
So if my total winning days = $1000 and my total losing days = $1500, I have to claim it as "$1000 -$1000". Not "$1000 -$1500". Plus if it's +$1000 and -$1000, that's what you must claim. Not just "$0."
Same with a profit. If my figures are +$2000 and -$1900, that's how I claim it. NOT just +$100.
There's a really cool book that really helped me with this stuff and it's especially for poker players. Check my review here: http://stickspoker.blogspot.com/2008...our-poker.html