What if someone get the bonus every month and it is not the same amount, for example 400-600 dollar. Is it still 25% flat tax? If that's the case than after all the deduction for a 600 dollar bonus you don't get 350+/-.. You see 250-/+ tax for 600 dollar, outrages don't you think. I think it is individuals responsibility to do the yearly adjustment for taxes, not monthly and of course not the payroll department.