Leave Loading on Annual Leave is tax free upto a certain threshold ($320).
Example
An employee is entitled to 4 weeks a year in annual leave. He takes his holidays 1 week at a time spread out of over the whole year.
The first time he takes a week holidays his pay is $671.43 gross. Of this $100 is attributed to leave loading.
The other three weeks are taken within the same financial year and are paid in the same way. Each time leave loading is paid it accrues in a balance kept in the employee's details. The field is called 'Leave Loading YTD' and can be found in the Balances 3 TAB of the employee's details. See Balances TAB
So by the third week of holidays the leave loading YTD figure is $300. The leave loading hasn't been taxed yet as the YTD figure hasn't pushed past $350. But in the fourth week of holidays the leave loading YTD goes to $400 and hence the tax kicks in and so the $100 of leave loading in that pay gets taxed, whereas in the three previous pays it wasn't.
To see how leave loading paid just by itself, apart from annual leave see PSB0019