.....I for one believe I can do better holding on to my own money for the year then the govt can.
The number thing is because some have a hard time saving it...if it lands in the paycheck they would spend it. Or some are actually afraid to zero out withholdings because it is the IRS they are dealing with.
So for those who don't know HOW to do this, tell your employer (who must do what you ask with regard to this process) that you want to change your withholdings. After you compute what your tax is by finding a percentage of tax compared to what you earned, and assuming your income will be about the same (IRS says that if you get within 10% of actual amount you owe, they are happy) you can then figure that 2013 taxes will be about the same as 2012 and if you get paid say, every other week, that is 26 weeks, take 1/26 of the tax amount and have that amount withheld from your paycheck as what you owe.
Then take the other 10% you would have otherwised paid and have it directly deposited into a savings account by your employer. It will gain interest, and at the end of the year, you won't be waiting on a refund to get it....because it will already be sitting in your savings account ready for you to spend it on a new sled.