Employees → Taxes → Federal tab
This is a very unusual circumstance; we recommend requesting written/signed direction from the employee in these cases to keep on file for your records, as there is the potential for underpayment penalties for not paying enough of the total estimated tax.
The figures are typically calculated by a CPA or accountant for employees who would prefer an alternative flat amount for their Federal Income Tax. When an employee would prefer an ALTERNATIVE flat dollar amount for Federal Income Tax, turn the Block Tax slider to Yes, and Save.
Using the Add’l Withholding ($) field, input the exact dollar amount to be withheld for Federal Income Tax each payroll run.
(Continue in Federal Tax: Pre-2020 W-4)