Yes. The law requires that all goods – whether second hand or new, commercial or private – be subject to the assessment of customs duty and GST and checked for community protection risks.
Duty and/or GST is only collected on imported goods where the value of the goods is above A$1000, OR where the goods include alcohol, tobacco or are prohibited/restricted products. Goods valued above A$1000 must be cleared through Customs by completion of a formal Customs Entry.
If you have received a Customs Notice then the shipper has already advised customs that your goods meet these criteria.