“Tax breaks on superannuation earnings and contributions are not the largest tax expenditure but the government’s move could be seen as a harbinger of other measures that similarly target a smaller population or group of entities that are seen to be well off,” he said.

Mr Molesworth said Treasury’s Tax Expenditures and Insights Statement shows the 50 per cent capital gains tax (CGT) discount for assets owned for more than 12 months would cost $23.7 billion this financial year, while the main residence CGT exemption will cost $48 billion.

“The CGT main residence exemption is the single largest tax concession provided,” he said.

“Some trimming of it could be on the agenda, if the government thinks that the increased tax revenue is worth the political pain.

“To limit the impact to a small group of taxpayers, a prospective change, only applying to increases in value from the time of the budget and where the property sells for more than $2 million might be palatable.”

He added that the CGT discount could be on the chopping block for some taxpayers.

“It’s possible to imagine a reduction in the discount for gains over a certain threshold – say $3 million – limiting the impacts to a smaller, wealthier cohort,” he said.

With Treasurer Jim Chalmers mulling over Treasury’s report on the $2 billion-a-year petroleum resource rent tax (PRRT), Mr Molesworth believes oil and gas producers should expect tax changes this year.

Keeping in line with measures that target a small but wealthier cohort, Mr Molesworth says small tweaks could still be made to the long-debated stage three tax cuts that are due to start in 2025.

“The government could still move to reduce the generosity of the stage three tax cuts by keeping the existing threshold for the top tax bracket at $180,000. Again, it would be framed at targeting high income earners and would not trouble the vast majority of the population,” said Mr Molesworth.

“What we probably don't expect to see are system-wide tax reforms that affect a large cohort of taxpayers or consumers.”

“On that basis, we don't expect to see any changes to the rate or the base of the GST, however acceptable or desirable those changes might be.”