I just started at a new company and received my first paycheck. It included a signing bonus, which of course made the paycheck much higher than a normal one will be. The fed withholding amount on the paycheck was much higher than I thought it would be, by a few percentage points.
How does payroll normally calculate the withholding amount? Obviously, the amount for the whole year can't be calculated, so it has to be predicted in a sense. But does payroll use the amount that they know is my annual salary, or do they do some sort math to simulate the gross pay on each paycheck being the same for the rest of the paychecks in a year?