Final answer:
The flat withholding rate for supplemental wage payments in 2018 is 22%.
Step-by-step explanation:
The flat withholding rate for supplemental wage payments in 2018 is 22%.
Supplemental wage payments are additional payments made to employees that are separate from their regular wages. These payments can include bonuses, commissions, severance pay, and other types of compensation.
When supplemental wage payment is paid separately or clearly indicated when added to regular wages, the withholding rate is 22% for 2018.