A $25,000 bonus on F-1 OPT in South Dakota nets you $19,500

Bonuses are "supplemental wages" under IRS Pub 15. The federal employer withholds a flat 22% on bonuses up to $1,000,000 cumulative per year (37% on the portion above that). FICA (Social Security 6.2% + Medicare 1.45%) applies to bonuses for F-1 OPT holders — except, in this scenario, NRA FICA exemption removes the SS/Medicare portion. South Dakota has no state income tax — $0 state withholding.

Bonus withholding is a flat rate, not your marginal rate — by IRS rule, employers withhold federal supplemental at 22% (or 37% above $1M cumulative) regardless of your bracket. That can over-withhold for low earners and under-withhold for very high earners. Your actual tax is reconciled when you file your 1040 in April: see our annual take-home pages for the marginal-rate view.

No — only the dollars above a bracket are taxed at the higher rate, and bonus withholding is a flat rate independent of brackets. The bonus increases your total annual income, which can shift your marginal bracket, but not retroactively re-tax earlier income.

Yes — if the 22% federal flat withholding exceeds your marginal effective rate, the excess is refunded when you file. The opposite (under-withholding) requires owing at filing. F-1 OPT holders in NRA status can also recover any FICA mistakenly withheld using IRS Form 843 — see the visa guide.