Paying GST to contractor on WT code via Payroll

We have a labour only contractor that I must deduct 20% withholding tax (building industry). The contractor is GST registered. There is no ability to pay the contractor through payroll so the withholding tax is accounted for in the Payday filing while also recognising his GST status and pay him his GST. Instead, I have had to create an item as a tax free addition to add the GST in payroll, then do a general journal entry to reverse the expense and reaccount for it as a GST purchase. The solution is for payroll to allow for GST registered contractors on the WT code.