That is what they say, but in fact you begin to repay when your weekly income is goes above $1057 (the equivalent og $55k p.a.) An unemployed friend of mine (who is not on the dole) managed to get a months contract work at about $1500 per week, so only earned about $6K for the entire year as that was his only income - he had Hecs repayments taken out of his pay.
Garry

