I have 4 sick days that i get paid for at the end ...

Not all companies Have paid sick days! They are considered a perk or a bonus that they do not have to offer you. Be gratefull that your company can offer them to you if you need them. The tax differance is not controled by the companies policies, but by the I.R.S.

Susan - Because this is pay above your regular pay, it's treated as a bonus on your paycheck. But don't worry, when you fill out your income taxes, it's treated just the same as all other wages, so if too much was held out of that check, you'll get it back after you file your taxes.