No Australian law requires your business to hold ISO certification. It is a voluntary standard, not a legal obligation. But that clean answer hides three things worth understanding: the safety laws that are mandatory, the technical standards that can be, and the contracts that make ISO effectively compulsory even though no statute does.
Keuer Solutions is an independent HSEQ consultancy. ISO certification is issued by JAS-ANZ accredited certification bodies, not by Keuer Solutions. We also run SWMS Aus, an online store selling SWMS and HSEQ template packs for Australian trades.