Employee bonuses can be a meaningful way to recognize performance, reward retention, or share company success. However, bonus payments also create payroll tax questions for employers and employees, especially when the net amount received is lower than expected.

For federal income tax withholding purposes, bonuses are generally treated as supplemental wages. This does not mean bonuses are taxed separately from other income on the employee’s annual tax return. Instead, it means employers may need to use specific withholding methods when processing the payment through payroll.

Understanding how supplemental wage withholding works can help employers communicate clearly with employees, process payroll accurately, and plan bonus payments with fewer year-end surprises.

What Are Supplemental Wages?

Supplemental wages are wage payments made to an employee that are not regular wages. According to the Internal Revenue Service (IRS), this category can include bonuses, commissions, overtime pay, severance pay, awards, prizes, back pay, retroactive pay increases, reported tips, taxable fringe benefits, and certain expense allowances paid under a nonaccountable plan.

In practical terms, a bonus is usually considered supplemental wages because it is paid in addition to an employee’s regular hourly wages or salary. Employers may pay bonuses separately from regular payroll or combine them with a regular paycheck. How the payment is structured affects the withholding method available.

Are Bonuses Taxed Differently?

A common misconception is that bonuses are “taxed at a higher rate.” For employees, the bonus is included in taxable wages and reported on Form W-2 along with other compensation. The employee’s actual income tax liability depends on total taxable income, filing status, deductions, credits, and other factors for the year.

The difference is withholding. Bonus payments may be subject to supplemental wage withholding rules, which affect how much federal income tax is withheld when the bonus is paid. Withholding is a prepayment toward the employee’s annual tax liability, not a separate final tax.

When Can Employers Use The 22% Supplemental Withholding Rate?

For supplemental wages of $1 million or less paid to an employee during the calendar year, employers may generally use the optional flat federal income tax withholding rate of 22%, provided the supplemental wages are separately identified and the employer withheld federal income tax from the employee’s regular wages during the current or immediately preceding calendar year.

This method is often used for stand-alone bonus checks because it is straightforward from a payroll processing standpoint. For example, if an eligible employee receives a $5,000 bonus and the employer uses the flat supplemental withholding method, federal income tax withholding on the bonus would generally be $1,100 before considering Social Security, Medicare, state withholding, local withholding, or other payroll deductions.

Employers should remember that the 22% rate applies only to federal income tax withholding. Bonuses are also generally subject to Social Security, Medicare, and Federal Unemployment Tax Act taxes.

When Is The Aggregate Method Used?

The aggregate method may apply when supplemental wages are paid with regular wages or when the employer chooses not to use the flat supplemental withholding method.

Under this approach, the employer combines the bonus with regular wages and calculates withholding as if the total were a single wage payment for the payroll period. The employer then subtracts the tax already withheld, or to be withheld, from regular wages and withholds the remaining amount from the supplemental payment.

The aggregate method may produce a different withholding amount than the 22% flat method. Depending on the employee’s Form W-4, regular wages, payroll frequency, and bonus amount, the aggregate method may result in more or less withholding than the flat rate approach.

What Happens When Supplemental Wages Exceed $1 Million?

A different rule applies when an employee receives more than $1 million in supplemental wages from an employer during the calendar year. The portion of supplemental wages that exceeds $1 million is subject to mandatory federal income tax withholding at 37%, without regard to the employee’s Form W-4.

For this threshold, employers may need to consider supplemental wage payments across related businesses under common control. This can be especially important for companies with related entities, shared executives, or compensation arrangements across commonly controlled businesses.

Bonus Withholding & Payroll Taxes

Federal income tax withholding is only part of the payroll tax picture. Bonus payments are generally subject to the same employment taxes as regular wages, including:

• Social Security tax
• Medicare tax
• Additional Medicare Tax when applicable
• Federal Unemployment Tax Act tax
• Applicable state and local payroll taxes

 
For 2026, the Social Security tax rate is 6.2% for the employee and 6.2% for the employer, up to the Social Security wage base limit of $184,500. The Medicare tax rate is 1.45% for the employee and 1.45% for the employer, with no wage base limit.

Employers also must withhold the 0.9% Additional Medicare Tax from wages paid to an employee in excess of $200,000 in a calendar year. This additional tax applies only to the employee portion.

When Should Employers Use Supplemental Withholding?

Supplemental withholding is commonly used when an employer pays compensation outside normal wages, such as:

• Performance bonuses
• Holiday bonuses
• Retention bonuses
• Signing bonuses
• Commissions
• Severance payments
• Awards and prizes
• Back pay or retroactive wage increases

 
The 22% flat method may be a practical fit when the bonus is separately identified, the employee has had federal income tax withheld from regular wages during the current or immediately preceding calendar year, and the employee’s supplemental wages are $1 million or less for the year.

The aggregate method may be needed or preferred when the bonus is combined with regular wages, the payment is not separately identified, or income tax was not withheld from the employee’s regular wages during the current or immediately preceding calendar year.

Because payroll facts can vary, employers should review the payment type, payroll setup, employee Form W-4 status, year-to-date supplemental wages, and state withholding rules before processing bonuses.

Common Bonus Payroll Mistakes To Watch

Even when the federal rules appear straightforward, bonus payroll can create issues if details are missed. Common areas to review include:

• Classifying the bonus as supplemental wages when applicable
• Separately identifying the bonus in the payroll system
• Tracking year-to-date supplemental wages for high earners
• Applying Social Security and Medicare taxes correctly
• Accounting for Additional Medicare Tax when wages exceed the threshold
• Reviewing state and local withholding requirements
• Communicating that withholding is not the same as final tax liability
• Coordinating bonus timing with year-end payroll deadlines

 
Employers with multistate employees or related entities may need additional review because state withholding rules, local taxes, and common-control considerations can affect payroll processing.

How Employers Can Communicate Bonus Withholding To Employees

Employees often focus on the net bonus amount, so clear communication can reduce confusion. Employers may want to explain that bonus checks often have a different withholding calculation than regular paychecks because bonuses are supplemental wages.

A simple employee-facing explanation could say:

“Bonus payments are generally treated as supplemental wages for payroll withholding purposes. Federal income tax withholding may be calculated using the IRS supplemental wage withholding rules, and Social Security, Medicare, state, local, and other applicable deductions may also apply. The amount withheld from a bonus is not necessarily the employee’s final tax liability for the year.”

This type of communication can help employees understand why the take-home amount may differ from expectations without providing individualized tax advice.

Planning Considerations Before Paying Bonuses

Before issuing bonuses, employers should coordinate with payroll, human resources, and tax advisors to review:

• Whether the bonus will be paid separately or with regular wages
• Whether the flat supplemental withholding method or aggregate method will be used
• Whether any employee is near or above the $1 million supplemental wage threshold
• Whether state or local rules require a different withholding approach
• Whether the bonus affects retirement plan contributions or benefit calculations
• Whether the payroll system is set up to code the payment correctly
• Whether employee communication is needed before the payment date

 
Year-end bonus planning is also a good time to review broader payroll processes. KPM CPAs & Advisors offers tax services and payroll-related support for businesses that want to strengthen compliance, reporting, and planning around employee compensation.

Bonus Withholding FAQs

Are bonuses considered supplemental wages?

Yes. Bonuses are generally considered supplemental wages because they are paid in addition to regular wages. The IRS lists bonuses among the examples of supplemental wages.

Is the federal bonus withholding rate 22%?

The optional flat federal income tax withholding rate for supplemental wages of $1 million or less is 22%, when the payment qualifies for that method. Supplemental wages above $1 million are subject to withholding at 37% on the excess amount.

Does the 22% rate cover all bonus taxes?

No. The 22% rate applies to federal income tax withholding only. Bonuses are also generally subject to Social Security, Medicare, Federal Unemployment Tax Act, and applicable state or local taxes.

Why was more tax withheld from my bonus than expected?

Bonus checks may have federal income tax withholding calculated under supplemental wage rules. In addition, Social Security, Medicare, Additional Medicare Tax when applicable, state tax, local tax, retirement contributions, and other deductions may reduce the net payment.

Is bonus withholding the employee’s final tax?

No. Withholding is a prepayment toward the employee’s annual tax liability. The final tax result depends on the employee’s full-year tax situation, including total income, deductions, credits, filing status, and other items.

Review Your Bonus Payroll Approach

Bonus payments can support employee retention and performance goals, but they also require careful payroll tax handling. Before issuing bonuses, employers should understand when supplemental wage withholding applies, which method fits the payment, and how the payment affects employment taxes and reporting.

If your business is preparing for bonuses, commissions, or other supplemental wage payments, KPM can help you evaluate your payroll tax approach and plan ahead.