How Pennsylvania withholds on a bonus
Pennsylvania withholds a bonus at 3.07%, the flat rate that applies to every dollar of compensation with no deduction or exemption, and has no separate supplemental figure. One widely copied payroll table lists Pennsylvania's supplemental rate as 5.99%; that is Rhode Island's rate, misplaced, and the Department of Revenue's rate is 3.07%. On a $10,000 bonus the percentage method withholds $2,200 federal, $620 Social Security, $145 Medicare and $307 Pennsylvania, leaving $6,728 before local tax.
Local earned income tax also applies to a bonus: about 1% in most municipalities ($100 on $10,000), 3% in Pittsburgh, and Philadelphia's wage tax of 3.74% for residents and 3.43% for non-residents ($374 or $343). None is included here. The aggregate method changes nothing on the Pennsylvania line and raises the federal line to about $2,700 for a $60,000 earner paid every two weeks.
What the withholding means for your Pennsylvania return
Pennsylvania's 3.07% on a bonus is exactly the tax owed on it, so the state line settles even. Any refund is federal: a $60,000 single filer's marginal federal rate is 12% up to $50,400 of taxable income and 22% above, so a $10,000 bonus is really taxed at about $1,450 federal against $2,200 withheld, and roughly $750 returns. New Jersey residents who earn a bonus in Pennsylvania are withheld for New Jersey under the reciprocal agreement, though Philadelphia's non-resident wage tax still applies in the city. The Pennsylvania paycheck calculator shows the marginal rates for any salary.