If the HECS repayment amounts do not accurately align with the reported income, enter the appropriate value in the Number of Dependent Children and Students field. If there are no dependent children or students, enter 0 in this field and recalculate the return.
The HELP debt is not calculated in the tax return that have the following:
Reduced Medicare Levy and if the taxpayer is entitled to this.
Dependent children information entered under IT8, the number of these affects payments.
For further information refer to ATO link: ATO- Compulsory Repayments.