According to
Tax Foundation, the IRS has added a new regulation, 26 C.F.R. § 31.3402(q), requiring that sponsors of poker tournaments withhold for taxes 25% of a players' winnings above $5,000. The sponsors must then provide this information to the IRS so that they can properly determine the taxpayer’s income tax liability. The regulation is set to take effect on March 4th 2008. However online and offshore poker games are not subject to the regulation.