[CORed]

If you win a bad beat jackpot or a tournament, they will make you fill out a W2-G. Live poker and house banked table games are not subject to this, as far as I know, but if you cash out (or buy in for) more than $10,000, they will file a Currency Transaction Report. It's easier to get away with non-reporting for cash games, if you're so inclined, because you are paid in cash. Online, you are going to have to make a bank deposit, which, while not reported to the IRS, does leave an audit trail that the IRS can find should they audit you. If they do, you are subject to penalties and interest on the unpaid tax, and possibly criminal prosecution, if they want to get nasty. Of course, if you are playing live games for high enough stakes that you are depositing winnings in a bank, or making large purchases, this can also be picked up by an audit. If you're winning a few hundred bucks now and then at the 5/10, and just using it for extra spending money, it's unlikely that the IRS will ever have a clue. Whether you report it or not is between you and your conscience.