No tax law against poker tournament | IXGAMES
A proposed rule that would have forced tournament poker players to give up 25 percent of their tournament winnings of $5,000 or more to the government will not go on the books. American tournament poker players could breathe easier because a proposal by the IRS to cipher off 25 percent of their tournament poker winnings will not be made into a tax law. Thanks to discussions between representatives of the American Gaming Association and IRS officials, this plan was killed. Now, players who gross $5,000 or more in a poker tournament will have to fill out a W2-G form immediately after they get paid. They are then responsible to pay taxes up to 30 percent of the winnings. The percentage depends on what tax bracket the player is in. 
If a player gives the casino false information, or if the casino fails to collect a W2-G form from its players, they are potentially responsible for paying the taxes.