Which of the following would not qualify as a supplemental wage payment?

Vacation pay is not considered a supplemental wage payment because it is typically treated as regular wages due to the nature of its purpose. Supplemental wages are defined as compensation paid in addition to an employee's regular salary or wages. These can include bonuses, overtime pay, commissions, backpay awards, and retroactive pay, as they serve as additional compensation for reasons beyond regular hours worked or standard compensation.

In contrast, vacation pay is given to employees for paid time off and is part of their normal compensation structure, rather than an additional payment for extra services or performance. While it is important for payroll processing, it does not fit the category of supplemental wages, which are often subject to different tax withholding rules.

The other payment types mentioned—backpay, retroactive pay, and bonuses—are often provided under unique circumstances, such as rectifying underpayment or rewarding performance, making them qualify as supplemental wages.