Retirement tax questions

When you take the withdrawal you don't pay the actual tax on it.  You have taxes withheld like from your paycheck.  The withholding is just an estimated amount.  At the end of the year you will get a form 1099R to enter into your tax return.  The withholding will be in box 4.  On your tax return you enter the full amount as income.  Then you get credit for the withholding on line 25b.