Notice to Deduct amounts owed to Inland Revenue NZ

I have read the previous thread but that doesn't help.  I have a letter from IRD asking for a total deduction of $171.00 from an employee.  The employee wants to make a one off payment to IRD and when I go to set up a deduction code in that employees payroll file, the set up asks for a choice between before tax or after tax.  I am presuming after tax.  I am on hold for for a call back from IRD as to whether we can do a one off payment instead of installments but thought I would ask here as well.  Thank you for any advice.