Bob’s taxable income would be $11,925, but then he gets a $5,000 bonus. 22% of the $5k is withheld, and then when he files his taxes the total taxable income is $16,925, so the actual rate of taxes he owed on that bonus was 12%, so assuming that his withholdings for all of his other income were exactly correct, he should get a refund for 10% of the $5k bonus, which would be $500.