> Is it stepped at all? Do you owe nothing before 50k and then once you cross that threshold you now owe money? That would seem to incentivise staying below that threshold for a percentage of borrowers.

Once you earn over the threshold your HELP repayments apply to your entire income. So, yes, at low incomes you get a pretty significant tax increase when you cross the threshold. I think they should make it marginal like regular income tax is...

https://www.studyassist.gov.au/paying-back-your-loan/loan-re...