The complete guide
Michigan bonus tax calculator: how it works
Bonuses are withheld at a flat 22% federally, then FICA, Michigan’s 4.25%, and any city income tax take their cuts. See the exact amount that reaches you.
A $5,000 bonus is not $5,000 in your pocket. Federal withholding treats bonuses as supplemental pay — a flat 22% comes off the top — and then FICA, the Michigan 4.25%, and your city’s income tax each take their share. This calculator runs your bonus through every layer so you know exactly what’s left.
How the 22% federal rule works
The IRS lets employers withhold on supplemental pay (bonuses, commissions, back pay) at a flat 22% — separate from your regular W-4 withholding. That’s the default "percentage method." There’s also the "aggregate method," where the bonus is blended with your last regular paycheck and withheld at your marginal rate — which can be more or less than 22% depending on your income. This calculator uses the standard 22% so your number matches the most common payroll setup.
FICA on a bonus
Social Security takes 6.2% and Medicare 1.45% on bonus dollars, exactly like regular wages — up to the $184,500 Social Security wage base and with the 0.9% Medicare surtax once your total wages pass $200,000. A big bonus late in the year can push you across the Medicare threshold, so the FICA line on a December bonus can be higher than on an identical January bonus.
Michigan and city tax on a bonus
Michigan applies its flat 4.25% to bonus income, and if you live or work in a taxing city, the city’s income tax applies too. Unlike the federal supplemental rate, Michigan doesn’t treat a bonus differently — it’s just more taxable income at the same flat rate. For a Detroit resident, a bonus loses 22% federal + 7.65% FICA + 4.25% state + 2.4% city before it reaches you.
A $5,000 bonus, worked through
Say you’re a Grand Rapids resident (1.5%) earning a $5,000 bonus. Federal supplemental: $1,100. FICA: $382.50. Michigan: $212.50. Grand Rapids city: $75. Total withheld: about $1,770 — leaving roughly $3,230, about 64.6% of the sticker amount. Change the city to Detroit and you keep about $3,110. The tool computes your exact figure with your settings.
When your bonus is paid matters
Because Social Security caps at $184,500 of wages, a bonus received after you’ve already hit that cap escapes the 6.2% — a real edge case that can materially change the number. Enter your full-year picture in the tool and check the FICA line to see whether your bonus is inside or outside the cap.