Assuming you are in the U.S., and you're talking about $100,000...
The Federal Government will withhold $28,000, although they will want for another $11,600 when you file your yearly return.
Your State Government may want as much as $11,000.
So, you get to keep about $50,000...unless the winnings puts you in a higher tax bracket - then you'll owe additional taxes on your regular income.
C'est la vie.
