Twenty-four of Australia's richest individuals were slugged an extra A$918m in taxes last financial year — an average of $38m each — following a crackdown on tax avoidance among ultra-high net-worth individuals.

Tax commissioner Michael Carmody, launching his annual report for 2001-02, said the sum included $451m in penalties for fraud and evasion. He said the Australian Tax Office was focusing on the use of offshore tax havens to hide income, as well as capital gains tax avoidance and intellectual property arrangements.

Carmody added that the ATO was being "especially vigilant" with ultra-high net-worth individuals, who often had access to high-level advice and sophisticated tax avoidance schemes.

"These results demonstrate our determination to responsibly pursue the more difficult and complex issues at the top end of the market," Carmody said.

The tax office announced in 1996 it would target tax evasion among what it terms the country's "high-wealth individuals" — those with assets of more than A$30m. The ATO identified 600 people in this bracket, who often paid disproportionately low levels of tax. It established a 100-member "high-wealth individuals task force" with the goal of investigating, understanding and policing high-level tax evasion.

"Our examination of high-wealth individuals and their associated entities has involved reviewing a number of tax planning arrangements, often tailored to the circumstances of the particular group," the commissioner's report said.

"During the year the task force carried out risk assessments on around 180 high-wealth individuals, including some newly identified individuals. A total of 24 cases were finalised, while 50 cases were in progress at June 30 2002."

A spokeswoman for the ATO said this was just the start of an ongoing campaign to identify and address the tax planning arrangements of high-wealth individuals.

"We will continue to expand our understanding of tax planning techniques used by high-wealth individuals and their associated entities through our task force," she said.

As part of this campaign, the ATO appointed Tony Pagone, a leading Melbourne tax lawyer and Victorian Supreme Court judge, to a full-time position in May. Pagone's role is to develop and clarify the interpretation of the law on "significant and complex" tax issues.

"Justice Pagone has practised extensively in the area of taxation law and has represented the Tax Office and taxpayers in a large number of matters involving the most complex areas of taxation laws," Carmody said.

Despite the nearly A$1bn of extra revenue the ATO has claimed in its annual report though, Carmody admitted only A$8m in the amended assessments had been agreed to. The remaining A$910m is still under dispute and will go before the courts.

"Given the complexity of the issues encountered, the bulk of the taxes raised are in dispute and the ultimate collections will depend on decisions of the courts," he said.

While the ATO would not reveal the 24 individuals who had been issued 'amended assessments' in the last financial year, one prominent HNWI has spoken out about his tax woes.

Harry Triguboff, a Sydney-based apartment builder, is attempting to settle with the ATO for a reported A$200m, which suggests the actual amount in dispute is significantly higher. BRW magazine, which publishes an annual Australian 'rich list', has estimated Triguboff's overall wealth at A$1.4bn.