The leave balances don't have to be shown on the payslip. But the accrued leave is an entitlement of the employee, and they are allowed to use if they have a legitimate need. So Moz is right - the leave balances do need to be readily available to the employee, they can't be kept secret. The advantage of having the balances printed on the payslip is that
HR staff don't have to spend time providing the same info by phone or email.