So If I made 1 million in the stock market, what taxes would be taken out?

[tro]

no the financial houses the handle your stock transactions do not withhold taxes
they issue you a 1099B on the proceeds, which does not mean that is the money you made on the stocks, on the amount they credit you as receiving
you want to make sure you have your purchase prices and dates of all your sales to arrive at your real profit or loss
and if you conduct this stock activity throughout the year, you would have been declaring on a 1040ES each quarter what you anticipate your income tax will be