Hello all, and forgive my amateur financial knowledge. I suppose that mathematically, the best way to do your taxes is to have as little withheld from your paycheck as possible, and to pay it all in at the end. This way you can potentially make (typically low-risk) investments with the money in the meantime. However, I do not understand how the allowances/withholdings work. Every website I go to just gives information about how to calculate these based on dependents and spouses and such. They don't say the actual mathematical effect. So, what is the effect of these numbers mathematically? Also, what are the limits, if any, on the numbers that one can put here?