How Wisconsin withholds on a bonus
Wisconsin's withholding guide (Publication W-166) publishes a tiered supplemental table rather than a single rate: 3.5% for annual wages up to about $15,000, 4.4% to about $52,000, 5.3% to about $333,000 and 7.65% above, the same thresholds as the income tax brackets. In practice that is the aggregate method: the bonus is withheld at the rate the earner's total wages fall in. For a $60,000 single filer that is mostly 5.3%, about $530 on a $10,000 bonus, alongside $2,200 federal, $620 Social Security and $145 Medicare under the percentage method, leaving roughly $6,505. There are no local income taxes in Wisconsin.
The calculator applies Wisconsin's brackets to the combined paycheck for the state line under both federal methods; the federal line rises to about $2,700 under the aggregate method for a $60,000 earner paid every two weeks.
What the withholding means for your Wisconsin return
Because the tiers track the brackets, the state line on a Wisconsin bonus is close to the tax owed, though Wisconsin's sliding standard deduction (which shrinks as income rises) can make the final figure a little higher for earners near its phase-out. Any refund is federal: a $60,000 single filer's marginal federal rate is 12% to 22% against 22% withheld, so roughly $750 returns on a $10,000 bonus. Illinois, Indiana, Kentucky and Michigan residents who earn a bonus in Wisconsin are withheld for their home state under reciprocity; Minnesota residents are not. The Wisconsin paycheck calculator shows the marginal rates for any salary.