What percent of Mega Millions lottery winnings are taxed?

15% Like most things the what was done to produce the income is irrelevant....except for Capital Gains on Investments (which many have tried to make lottery winnings and lost in court), all are taxed the same. Winnings are ordinary income. You will pay taxes at whatever rate is determined by your total taxable income, and both Federal & State. If you can itemize, gambling losses are 100% deductible up to the amount of winnings. Don't forget those lotto tickets