If you’re self-employed you need to make your own student loan repayments. How much your repayments are depend on your adjusted net income. Your adjusted net income is your income minus expenses.
The end of year repayment for student loans is 12% for every dollar you earn over the annual repayment threshold (currently $19448).
You will need to complete a Student Loan interim payment estimation (SLE3) and send this to the IRD. They will let you know if you have any repayments to make on your student loan.
You can find more information on managing your student loan here