See how your bonus is actually taxed. Compare the flat 22% withholding rate against your real marginal tax rate to know if you will get a refund or owe more.
Most employers withhold federal tax on bonuses at a flat 22% rate (37% for amounts over $1 million). This is called the "percentage method" and is simply a withholding convenience — it is not your actual tax rate on the bonus.
Your real tax on the bonus depends on your marginal tax bracket. If your combined salary and bonus push you into the 24% bracket, the flat 22% withholding under-withholds and you will owe the difference at tax time. If you are in the 12% bracket, the 22% rate over-withholds and you will get a refund.
FICA taxes (Social Security at 6.2% and Medicare at 1.45%) apply to bonuses the same way they apply to regular wages, up to the Social Security wage cap of $176,100. These are withheld regardless of the method used for income tax.
State taxes on bonuses vary by state. Some states use the same flat withholding approach, while others tax bonus income at your marginal state rate. States with no income tax obviously do not apply here.