Hi:

This chart may help you.

http://finance.toolbox.com/blogs/quickbooks-tips/how-to-enter-payroll-prepared-by-an-outside-payroll...

On your books you will be posting the amount that is withheld from the employee's payroll as a credit to a liability. (Garnishments Payable or whatever you want to call it). When you issue the check in payment of the garnishment, you would post the debit to the same account. The balance should zero out after each payment.

Hope this helps.