Tax havens under scrutiny

The tax office is to use an informer's tip that some of the nation's richest people use offshore havens to avoid Australian tax.

Australians worth more than $30 million could face criminal charges, with tax officials believing five of them still use Swiss banks to hide millions in cash.

And thousands more people, including those with at least $5 million, could be caught in a global sweep that includes Vanuatu and other tax havens.

The Australian Taxation Office is close to ending its Project DO IT program aimed at encouraging people with cash in offshore havens to bring their money back to Australia.

With a week before the operation ends, about 1750 disclosures have been made to the tax office, covering $1.7 billion in offshore assets and income of $240 million.

Another 800 people are expected to reveal holdings in the next nine days, with the tax office confident this will reveal at least as much secret income and assets.

But previously secret banking details an informant supplied puts the focus on some of the nation's richest people. It is understood the five high-wealth individuals are yet to contact the ATO under Project DO IT. It leaves them open to ATO penalties that could stretch over a decade of evasion and end with charges over accounts in Switzerland.

A tax sharing treaty was signed with Switzerland giving ATO officials the chance to find out more about Australian holdings there.

Deputy tax commissioner Michael Cranston said the ATO would target those who had not come forward about secret overseas holdings.

"If you have an undisclosed bank account in Switzerland and you don't make a disclosure under Project DO IT, there is a good chance we will be requesting information about you," he said.

Apart from the informant's information, the ATO has records on 2000 Australians with bank accounts in Vanuatu that are being checked against tax records.

Another 120 people were identified in another recent tip-off.