How do I specify additional tax withholding during payroll runs for the US?

Each federal or state component on the Tax Withholding Card has fields for specifying additional withholding during payroll runs.

For this tax	Use this field	Notes
Federal income tax (FIT)	Extra Withholding	If multiple pay runs occur during a pay period, the payroll process withholds the extra withholding amount only once. If an exempt employee enters an extra withholding amount, the payroll process ignores the amount.
State income tax (SIT)	Additional Tax Amount	If multiple pay runs occur during a pay period, the payroll process withholds the extra withholding amount only once. If an exempt employee enters an extra withholding amount, the payroll process ignores the amount. The payroll calculations apply the additional tax amount after it calculates any residence SIT credit from work SIT.