From 18th November 2017 relevant health authorities will now notify the Department (DIBP) if you have an outstanding health debt.
Condition 8602 provides "the holder must not have an outstanding health debt".
You may be on a temporary visa such as Student (subclass 500), Temporary Employment (subclass 457), Skilled Regional (Provisional subclass 489).
A breach of this condition can result in cancellation of your temporary visa and could put you at risk of the refusal of a future visa grant because of the breach.
This will only apply to debts incurred after 18th November 2017.