How a bonus is withheld in South Dakota
South Dakota has no state income tax and no local income taxes, so a bonus loses only the federal lines: income tax withholding at the flat 22% supplemental rate (or under the aggregate method), Social Security at 6.2% up to the $184,500 wage base, and Medicare at 1.45%. On a $10,000 bonus the percentage method withholds $2,200, $620 and $145, leaving $7,035. South Dakota has no employee-funded disability or leave premium either, so nothing else appears on a bonus stub.
Under the aggregate method the bonus is added to a regular paycheck and federal withholding is computed on the combined amount under the normal tables; for a $60,000 earner paid every two weeks that withholds about $2,700 rather than $2,200 on a $10,000 bonus, and the extra comes back at filing. The tax owed is identical under both methods.
What the withholding means for your federal return
A single filer on $60,000 has a federal marginal rate of 12% up to $50,400 of taxable income and 22% above it, so a $10,000 bonus is really taxed at about $1,450 against $2,200 withheld, and about $750 returns as part of the refund. South Dakota residents who earn a bonus for work in Minnesota, Iowa or Nebraska are withheld for that state on it. The South Dakota paycheck calculator shows the federal marginal rate for any salary. A South Dakota bonus appears on the W-2 with the state boxes blank, and no state return is filed; the only reconciliation is on the federal Form 1040.