If your winnings are reported on a Form W-2G, federal taxes are withheld at a flat rate of 24%. If you didn't give the payer your tax ID number, the withholding rate is also 24%.
How much are lottery winnings taxed? If you win nearly a billion dollars in the lottery, you definitely owe federal income tax on it. To start, 24% of your winnings are withheld for the IRS.