FAQs: borrowers questions and answers: only income is unearned but I have an SA return
If you receive an SA return and Student Loan repayments are due you will then make your payment along with the balancing payment for tax and NICs on or before 31 January following the end of the tax year.
When you receive your SA return at the end of the year you should complete it in the normal way as regards tax.
However, the return will also contain boxes to confirm that you are a Student Loans borrower and to enter the amount of repayments due.
If the only income on the return is unearned then you may be liable to make repayments if the total income exceeds the threshold during the year.