The two methods
How does the flat 22% method work?
When supplemental wages are paid separately from regular wages (or identified separately on the pay stub), the employer can withhold a flat 22% for federal income tax. No W-4 information is needed for this calculation — the rate is the same for everyone regardless of filing status, allowances, or actual bracket.
This simplicity is why the flat method is popular with employers. But it creates a mismatch for many workers: if your real marginal rate is 12%, the 22% over-withholds by 10 percentage points on every supplemental dollar. If your rate is 32%, it under-withholds by 10 points. The difference is reconciled when you file your annual return.
For supplemental wages exceeding $1 million from a single employer in a calendar year, the mandatory rate jumps to 37%. This applies to the excess above $1 million only.
How does the aggregate method work?
The aggregate method is more complex but sometimes more accurate for high earners. The employer:
- Adds the supplemental wages to the most recent regular paycheck
- Treats the combined amount as a single regular wage payment
- Calculates withholding on the combined amount using the W-4 and bracket tables
- Subtracts the withholding already calculated on the regular wages alone
- The remainder is the withholding on the supplemental portion
This method can withhold more or less than 22% depending on the employee’s situation. For moderate earners receiving a large one-time supplement, it typically withholds more than 22% because the inflated paycheck is annualized into a higher bracket.
What is NOT a supplemental wage?
Not all non-salary payments are supplemental wages. The following use regular wage withholding (bracket-based, using the employee’s W-4):
- Shift differentials (night, weekend, holiday premiums) — see shift differential tax rules
- On-call/standby pay that is part of the regular schedule
- Hazard pay and environmental differentials
- Regular salary increases retroactively applied (though some employers treat retro pay as supplemental)
And these are not wages at all (different tax treatment entirely):
- Per diem under an accountable plan — excluded from income
- Workers compensation — tax-free
- Unemployment benefits — taxable but no FICA, voluntary W-4V withholding
- Pension/annuity income — W-4P/W-4R withholding, no FICA
- Jury duty pay — other income, no FICA
FICA on supplemental wages
All supplemental wages that are employment wages are subject to FICA at the same rates as regular wages:
| FICA component | Rate | 2026 limit |
|---|---|---|
| Social Security | 6.2% | $184,500 wage base |
| Medicare | 1.45% | No cap |
| Additional Medicare | 0.9% | Above $200K (single) / $250K (MFJ) |
If your year-to-date wages have already exceeded the Social Security wage base, additional supplemental wages are exempt from the 6.2% SS portion — only the 1.45% Medicare (and possibly 0.9% additional) applies. See the FICA tax explained page for details and the FICA calculator for your numbers.
Explore by income type
Each income type has unique rules. Use the guides below for the specific type you are looking for:
- Employment extras: Overtime tax · Commission tax · Shift differential · PTO payout · Seasonal job withholding
- Special payments: Bonus tax · Signing bonus · Severance tax · Settlement tax · Relocation tax
- Self-employment: 1099-K gig worker · Honorarium · SE tax calculator
- Non-cash / fringe: Imputed income · Per diem rules · Stipend rules
- Benefits: Unemployment tax · Workers comp · Disability insurance
- Retirement: Pension withholding · Social Security tax · Retirement income tax
Questions
Supplemental wages FAQ
What are supplemental wages?
Supplemental wages are compensation that is not part of an employee's regular wage payment. The IRS defines them in Publication 15 to include bonuses, commissions, overtime pay, severance pay, back pay, retroactive pay increases, taxable fringe benefits, sick pay by a third party, and reported tips. Supplemental wages are subject to special withholding rules: either a 22% flat rate or the aggregate method.
What is the federal supplemental wage withholding rate?
The federal supplemental wage flat withholding rate is 22% for 2026. This rate applies to supplemental wages up to $1 million paid by a single employer in a calendar year. For supplemental wages exceeding $1 million, the mandatory withholding rate is 37%. These rates are set by IRS Publication 15 and apply to federal income tax withholding only; FICA taxes are calculated separately.
What is the difference between flat and aggregate withholding?
The flat method withholds a straight 22% on the supplemental wages. The aggregate method combines the supplemental and regular wages for the pay period, calculates withholding on the total as if it were a single regular payment, then subtracts the withholding already calculated on the regular wages alone. The aggregate method often withholds more than 22% for moderate earners because it annualizes the inflated pay period.
Does the 22% rate mean supplemental wages are taxed at 22%?
No. The 22% is a withholding rate, not a tax rate. Your actual tax on supplemental wages depends on your marginal tax bracket, which is determined by your total annual income. If you are in the 12% bracket, the 22% withholding over-withholds and you get a refund. If you are in the 32% bracket, it under-withholds and you may owe at filing time. Withholding is an estimate; your actual tax is calculated when you file.
Which income types are NOT supplemental wages?
Regular wages, shift differentials, on-call pay, and hazard pay that are part of the employee's recurring pay schedule are generally not supplemental wages. Per diem under an accountable plan, workers compensation, and employer health insurance contributions are also not supplemental wages. These use regular bracket-based withholding or are excluded from income entirely.
- Sources: IRS Publication 15 (2026) · IRS Publication 15-T · SSA 2026 wage base $184,500 · IRC Section 3402.
- 🔄 Last updated July 31, 2026 · Tax year 2026
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