In recognition of the importance and sacrifices associated with military service, many employers provide a supplemental payment for their employees called to active military service which covers the difference between their military pay and their regular compensation. Pay differentials are provided for varying lengths of time.

Revenue Ruling 2009-11 provides that a differential wage payment

Employers offering severance payment to employees are typically uncertain about the payroll taxes that may apply to these additional payments. Severance pay is treated as “supplemental wages” because it is not a payment for services in the current payroll period but a payment made upon or after termination of employment for an employment relationship that has