The IRS tracks gambling winnings primarily through Form W-2G, "Certain Gambling Winnings." Casinos and race tracks are legally required to issue this form to both the winner and the IRS if winnings exceed specific thresholds—typically $1,200 for slot machines, $1,500 for keno, or $5,000 for poker tournaments (minus the buy-in). Additionally, if your winnings are subject to federal income tax withholding (usually at a flat 24% rate), the IRS receives a record of that payment. Even if you don't receive a W-2G, you are legally obligated to report all gambling winnings as "Other Income" on your tax return. The IRS also uses sophisticated data-matching programs to compare your reported income against bank deposits and lifestyle indicators; if a casino files a Currency Transaction Report (CTR) for a cash payout over $10,000, that information is also shared with federal authorities.