According to the ATO website: Payments you must report | Australian Taxation Office:
"Payments made to contractors are not mandatory to report under STP. However, if you currently report contractors through your payroll solution, you should continue to do so under STP.
If you report payments to contractors and you have a voluntary agreement to have withholding applied, you don't need to provide a payment summary to these contractors.
If the contractors are managed outside of payroll using accounts payable, you don't have to report payments to them under STP."