The Australian Taxation Office is investigating funding payments for the landmark Gorgon natural gas project that will deliver estimated tax-free profits of more than $60 billion to partners Chevron, ExxonMobil and Shell over the life of the development.

The three partners book almost $3 billion in profits a year tax free, by charging their Australian arms for related-party loans at more than 10 times the interest rate that the majors paid to third-party lenders in the United States.