A personal expense to be deducted from the weekly pay

Hi

I sometimes get an employee asking for favours like paying for their personal expense like car registration. How do I process my reimbursement in the weekly pay so it gets deducted from their nett pay. How do I set up an item in the payroll so it shows a deduction that would be taken off from the nett pay.

I set up an item called Advance Payment but it is showing as a deduction from their Gross Pay when I do the STP Lodgement. The Gross amount shows incorrectly. It appears the Deduction is calculated against the Gross Amount in the STP screen.

I would appreciate if someone could show me how it is done correctly please.

Imogen