The Greens have proposed a new “tycoon tax” modelled on a former Labor policy. 

Greens leader Adam Bandt has announced a new plan to tax large companies and mining corporations to support dental appointments and mental health support, and lift the rate of JobSeeker payments.

The Greens' Corporate Super-Profits Tax mirrors Labor's controversial mining tax, which passed in 2012 but was later repealed by Tony Abbott as prime minister. 

It would see any company with a turnover of more than $100 million slugged with a 40 per cent corporate super-profits tax. 

The tax would be applied to net revenue, after income tax and a “fair return to shareholders” is deducted. 

“While everyone else has suffered through the pandemic, billionaire corporations have made out like bandits and profits are at record highs,” Mr Bandt said. 

“A 'tycoon tax' is essential because there's huge wealth in this country, but it's being hoarded by a greedy few.”

Economist Saul Eslake says it would be a big hit to companies. 

“In effect, they're saying that any company which generates profits that represent a return to shareholders in excess of 6 per cent, or thereabouts, after a payment of the normal company tax, should be paying an additional 40 per cent of those so-called excess profits to the government by way of tax,” he said.

Mr Eslake says Australia's corporate tax rate is already higher than many other countries, and may not be the best mechanism to bring about change.

“Among the 38 or so member countries of the OECD, only Portugal and Colombia, neither of which are particularly developed, have higher statutory corporate tax rates than Australia does,” he said. 

“Indeed, Australia gets a larger proportion of its total tax revenue from company tax than most other so-called Western economies.

“So the case for Australia to do more in that context is, I think, not very compelling.”

Official costings suggest the Greens’ policy would raise $338 billion over a decade.

“We should be firstly using this money to get dental fully into Medicare, mental health fully into Medicare, to help deal with some of the stresses of the pandemic,” Mr Bandt said. 

“That is going to go a long way to relieving the pressures on everyday people and making life better for all of us. 

“And if the billionaires and big corporations have to pay their fair share and pay a bit more to do that, I think most people would agree with that.”