Regardless of where you go to gamble, remember that your winnings are taxable income. You can,however, deduct your losses, up to the amount of your winnings, to help ease the tax bite.
IRS Publication 529 suggests you keep a gambling diary, recording your winnings and losses separately.
Actually, the IRS says you "must" keep such records if you want to guarantee that you meet reporting requirements and ensure your deductions aren't disallowed.
According to Publication 529, for tax purposes your gambling diary should contain at least the following information.
The date and type of your specific wager or wagering activity. The name and address or location of the gambling establishment. The names of other persons present with you at the gambling establishment. The amount(s) you won or lost.
In addition to your diary, you should also have other documentation. If you win enough, you'll get a Form W-2G, Certain Gambling Winnings, from the paying casino, track or other payor.
You also can verify your winnings by showing wagering tickets, canceled checks, substitute checks, credit records, bank withdrawals and statements of actual winnings or payment slips provided to you by the gambling establishment.
For certain wagers, the IRS also offers some specific record keeping suggestions.
Keno: Copies of the keno tickets you purchased that were validated by the gambling establishment, copies of your casino credit records, and copies of your casino check cashing records.
Slot machines: A record of the machine number and all winnings by date and time the machine was played.
Table games: Record the number of the table (blackjack, craps, poker, baccarat, roulette, wheel of fortune, etc.):at which you were playing. Casino credit card data indicating whether the credit was issued in the pit or at the cashier's cage.
Bingo: A record of the number of games played, cost of tickets purchased, and amounts collected on winning tickets. Supplemental records include any receipts from the casino, parlor, etc.
Racing: A record of the races (horse, harness, dog, etc.), amounts of wagers, amounts collected on winning tickets, and amounts lost on losing tickets. Supplemental records include unredeemed tickets and payment records from the racetrack.
Lotteries: A record of ticket purchases, dates, winnings, and losses. Supplemental records include unredeemed tickets, payment slips, and winnings statements.
I don't believe they currently specify online wagering as any different than offline wagering. However, it's up to you if you feel like letting them know that you are gambling online as an American Citizen
