For any deduction that will involve a background calculation, you want to use the Deduction Wizard. A few examples would be Child Support, Wage Garnishments, Tax Levys, etc. 

Navigate to the employee's profile

Select the employee

Navigate to the Deductions

Payroll > Deductions then select the ellipses to view the options available

Select Deduction Wizard from the drop down

Select the type of deduction from the drop down menu

Select NEXT 

From this point, you will fill out the proper information, add a vendor, and set an amount based on the type of deduction.

Anything with a red asterisk is going to be a required field.

Once you enter the required information, you will select Next, review the summary of information entered and select Finish