A $20,000 sign-on bonus is a powerful recruiting tool — right up until the new hire sees the deposit and wonders if there was a payroll error. There usually isn't. Sign-on bonuses get squeezed by a stack of withholding rules plus a quirk unique to starting a new job.
Why a sign-on bonus is hit hard
A sign-on bonus is a supplemental wage, so it follows the same rules as any bonus: a flat 22% federal withholding (37% above $1M), plus 7.65% FICA, plus your state income tax. In a high-tax state that's already 35%+ before the quirk below. For the full mechanics, see how bonuses are taxed.
The new-employer quirk
Social Security tax (6.2%) only applies up to an annual wage cap. Your new employer has no record of what you already earned and paid elsewhere this year, so it assumes you've earned $0 so far — and withholds the full 6.2% on your bonus even if you'd already hit the cap at your old job.
What actually comes back
Two things can return to you: over-withheld federal income tax (if 22% exceeded your real rate on that income) and excess Social Security from double-paying across employers. Both are settled on your tax return the following spring.
How to plan for it
- Budget the net, not the gross. Assume you'll see roughly 60–65% of a sign-on bonus up front.
- Watch for clawbacks. Many sign-on bonuses must be repaid if you leave early — read the agreement.
- High earner? Expect a possible bill, since 22% may under-withhold relative to your marginal rate.
Frequently asked questions
Why was my sign-on bonus taxed so heavily?
Flat 22% federal withholding, full FICA, and state tax all apply at once — and a new employer often assumes $0 prior Social Security wages, so more is withheld.
Do I get sign-on bonus taxes back?
Often partly. Over-withholding returns at tax time. But if you're a high earner, 22% may be too low and you could owe more.