Re: Ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha
What I never understand about US taxes is all this talk of "refunds". Why are so many people overpaying in the first place??
Assuming you're serious -- it's because the tax rate varies by your annual income and you're allowed to deduct certain expenses before the tax is calculated. A prorated part of your estimated tax is withheld from your weekly/biweekly/monthly paycheck. At the end of the year, all your deductions (unpredictable things like mileage, business and medical expenses) are deducted, any profits from investments are added (but these may be taxed at a different rate, depending on how long you've held the investments) and the actual tax due is calculated on the total.
So, you never know exactly how much tax you owe until the year's over, but you must pay an estimated tax (based on what you earned last year) during the year. Whatever's extra, you get back. Without interest, natch. If you've erroneously underpaid, you owe the difference, with interest, of course.
// death and taxes, and I'm not too sure about death
// ask Cratchitt, he knows