I’m 17 and I have a summer job umpiring baseball. Every check I pay into FICA and the Illinois State Income Tax. My most recent and also my largest check is the only time I’ve paid into the federal income tax. I made 99 dollars before taxes, and paid 1.44 in federal income tax which is the same amount I paid into Medicare. Why have I only paid into it once?
The withholding tables are set up in such a way that they assume every paycheck is the same paycheck you will receive throughout the year and withhold taxes accordingly. Since all of your other paychecks were smaller, it was assumed (if you had the same paycheck every pay period) you would owe no federal income tax and therefore nothing was withheld. If this larger check was the same for every pay period of the year, you would owe some tax and therefore some was withheld.
If at the end of the year you owe no federal income tax, you can file a return and have your withholding refunded to you.