Four of the world's largest companies have been under investigation by Australian tax authorities, amid new evidence from US executives about how Facebook, Google, Apple and Microsoft are shifting money to offshore tax havens.

Appearing before a highly anticipated public hearing into corporate tax evasion, the executives endured questions about why so much of the revenue generated in Australia ultimately ended up booked elsewhere.

Microsoft's corporate vice-president of worldwide tax, Daniel Goff, said some of the $1.8 billion revenue generated in Australia had been transferred to Microsoft's regional headquarters in Singapore and Ireland to fund research and development.

He also revealed the global tech giant had reached a last-minute confidential settlement with the ATO ahead of the hearing – a development Australian Taxation Office commissioner Chris Jordan described as "awfully coincidental".