If you win underR$5000, there is no withholding, but it's still potentially subject to taxes. If you win aboveR$5000, the casino or sportsbook must withhold 24% and is obligated to issue you Form W-2G, which will document their withholdings.

For Massachusetts purposes, losses (up to as much as winnings) aren't deductible even if they may be claimed as an itemized deduction on U.S. Form 1040 (Schedule A). The exception is gambling activities that are considered a trade or business or any gambling establishment in accordance with MGL Chapter 23K.