Increasing numbers of Australian small businesses operators are falling behind on tax and superannuation obligations, Tax Commissioner Rob Heferen has warned, as the ATO chases $50 billion in outstanding debts.

In one of his first major outings since taking over as head of the Tax Office in March, Mr Heferen told a Council of Small Business Organisations of Australia event on Thursday there was significant risk of businesses trading while insolvent in the wake of COVID-19 pandemic disruption.