Supplemental Wages

Supplemental wages are payments an employee receives outside their regular wages, such as bonuses, commissions, overtime, and severance. The IRS sets specific rules for withholding tax on them. Employers can apply a flat 22% rate or combine the payment with regular wages and withhold based on the employee’s W-4.

What Are Supplemental Wages?

Supplemental wages cover compensation that falls outside the steady paycheck. A year-end bonus, a sales incentive, an overtime payment, a severance package, or a payout of unused vacation all qualify. The IRS uses the category specifically to set withholding rules, because these payments do not fit neatly into the regular withholding tables built around a normal paycheck.

The distinction matters for one main reason: it changes how tax is withheld up front, not how much tax the employee ultimately owes. The withholding affects how much of the payment reaches the employee as net pay in the moment, but the final tax bill is settled when the person files their annual return. That is why a heavily withheld bonus often produces a refund later.

How Supplemental Wages Work

The IRS gives employers two main withholding methods:

• Flat-rate method: withhold a flat 22% on supplemental wages up to $1 million in a year. Any amount above $1 million must be withheld at 37%.
• Aggregate method: add the supplemental payment to the employee’s most recent regular wages, then withhold as if it were one larger combined payment based on the W-4.

The flat-rate method is simpler and predictable, which is why many employers use it for bonuses and commissions. The aggregate method can be more accurate for the employee’s actual situation but requires more calculation. Employers generally pick one approach and apply it consistently.

There are two conditions, though. The flat-rate method is only allowed when the supplemental wages are paid separately from regular wages, or are clearly identified on a combined payment, and when income tax was withheld from the employee’s regular wages at some point in the current or prior year. If those conditions are not met, the employer must use the aggregate method.

Beyond Income Tax: Other Withholdings

It is a common misconception that the 22% flat rate is the only thing taken out of a bonus. In reality, supplemental wages are also subject to Social Security and Medicare taxes, just like regular pay. So a bonus has FICA withheld on top of the income tax withholding, which is part of why a check can feel smaller than expected.

Certain non-cash perks treated as imputed income, such as the taxable value of some fringe benefits, can also be handled as supplemental wages for withholding purposes. The label is about how the payment is taxed at the source, not whether it arrives as cash.

Example

Priya earns a $5,000 year-end bonus. Her employer uses the flat-rate method, withholding 22%, or $1,100, for federal income tax. On top of that, Social Security and Medicare taxes come out, so Priya’s take-home is less than $3,900.

If Priya’s actual marginal tax rate for the year turns out lower than 22%, she recovers the difference as a larger refund when she files. The withholding is not a separate or extra tax, just a prepayment toward what she ultimately owes for the year. If her rate is higher than 22%, she may owe a bit more at filing instead.

Key Takeaways

• Supplemental wages are payments outside regular wages.
• Examples include bonuses, commissions, overtime, and severance.
• Employers can withhold at a flat 22% or use the aggregate method.
• Amounts over $1 million are withheld at 37%.
• Social Security and Medicare taxes also apply to supplemental wages.
• Withholding is a prepayment; over-withholding is refunded at tax time.

Frequently Asked Questions

What counts as supplemental wages?

Supplemental wages include bonuses, commissions, overtime, severance, awards, back pay, and payouts of accumulated leave. They are payments outside an employee’s regular wages.

How are supplemental wages taxed?

Employers can use the flat-rate method, withholding a flat 22% on amounts up to $1 million, or the aggregate method, combining them with regular wages and withholding based on the W-4.

Why was my bonus taxed so highly?

Bonuses are supplemental wages and are often withheld at the flat 22% rate, which can be higher than your normal withholding. Any over-withholding is settled when you file your return.

Are supplemental wages subject to Social Security and Medicare?

Yes. Beyond income tax withholding, supplemental wages are also subject to Social Security and Medicare taxes, just like regular wages.

What is the supplemental rate over $1 million?

Supplemental wages above $1 million in a calendar year must be withheld at the highest income tax rate, which is 37%, on the amount over that threshold.