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.