You earned a $10,000 bonus and expected a nice windfall. Instead, $3,800 disappeared before the money hit your account. Federal withholding took $2,200 (22%), Social Security took $620 (6.2%), Medicare took $145 (1.45%), and state tax took anywhere from $0 to $800+. Your $10,000 became roughly $6,200–$7,000 depending on your state. This is the bonus tax shock, and it hits every single time.
The IRS treats bonuses as ‘supplemental wages’ and gives employers two withholding methods. The percentage method — used by most payroll systems — withholds a flat 22% federal on bonuses up to $1 million (37% above $1 million). This is simple but crude: it doesn’t consider your actual tax bracket, marginal rate, or other withholdings. It’s just 22%, regardless of whether you earn $40,000 or $400,000.
The aggregate method is the alternative, and it’s why some bonus checks feel even worse. Your employer adds the bonus to your regular paycheck, calculates withholding on the combined total as if you earned that much every pay period, then subtracts the withholding already taken from your regular pay. If your $3,000 biweekly check suddenly becomes $13,000, the system temporarily thinks you earn $338,000/year and withholds at that rate. This can result in 30%+ federal withholding on the bonus portion.
Here’s the critical distinction most people miss: withholding is not your actual tax. Your bonus is taxed as ordinary income at whatever marginal rate applies to your total annual earnings. If you earn $80,000 salary plus a $10,000 bonus, that bonus falls in the 22% bracket — so the flat 22% withholding is actually right on target. But if you earn $45,000 and get a $5,000 bonus, the bonus is mostly in the 12% bracket. You were overwithheld and will get money back when you file.
FICA taxes on bonuses are inescapable and exact — there’s no ‘overwithholding’ issue. Social Security (6.2%) and Medicare (1.45%) apply to bonus income just like regular wages, up to the Social Security wage base of $176,100. If your salary plus bonus exceeds that cap, SS tax stops on the excess. Medicare has no cap and adds an extra 0.9% on wages above $200,000.
The bottom line: your bonus is not taxed at a higher rate than your regular income. It’s withheld at a flat rate for administrative simplicity, but your actual tax liability is determined when you file your return. If you’re in a bracket below 22%, you’ll get money back. If you’re above 22%, you may owe a small amount. Either way, the IRS settles up in April. Don’t let withholding shock discourage you from earning more.