High-income earners are likely to try to find ways to avoid the 2 per cent tax increase to repair the Budget, senior Treasury officials have conceded.
In comments that echo warnings by private economists in the wake of the Budget, a Senate estimates hearing has been told some highly paid Australians were likely to use business tax structures to avoid the levy.
The 2 per cent tax increase, expected to earn $3.1 billion, affects about 300,000 people in the top marginal tax rate who earn more than $180,000 a year.
But Treasury's revenue group executive director Rob Heferen said given the tax increase would be in place for 3 years, there was likely to be some efforts by high income earners to reduce their tax bill.
At the same time as the personal income tax rate goes up, the company tax rate is due to fall to 28.5 per cent.
Mr Heferen conceded there were ways people could avoid the 2 per cent levy.
A report by the Auditor-General has found that some of the nation's richest people are not paying a cent in tax. The auditor, examining the way the tax office has handled so-called high-wealth individuals, found extremely rich people posed a significant revenue risk.
In 2010 there were about 2600 people with wealth of at least $30 million.
According to the auditor, 5 per cent of these people - about 130 - did not pay any tax.
With the number of high-wealth individuals expected to climb sharply, the auditor said there were serious issues facing the tax office.