Yes. You can make a voluntary repayment to the ATO at any time and for any amount. Voluntary repayments are in addition to the compulsory repayments made through your tax return.
To find out how to repay, access via mygov, click on the reference link below, or call us on 0242295133 and we can give you the bpay codes.
Note: The 5% voluntary repayment bonus ceased on 1 January 2017.
Reference: http://studyassist.gov.au/sites/studyassist/payingbackmyloan/loan-repayment/pages/loan-repayment