The boss of Australia's biggest bank says the Albanese government's proposed capital gains tax changes should be limited to passive investments such as housing.

But Labor's proposal goes much further than the model backed by Mr Comyn, applying the changes across all major asset classes, including shares, property and businesses.

Commonwealth Bank chief executive Matt Comyn said he believed the tax overhaul should target wealth accumulated through passive assets rather than investments tied to innovation and business growth.

'I think that's the area you have to look at,' he told 7.30.

'This is a step where I do think wealth, particularly relative to labour and consumption, is taxed lightly and inconsistently.

'There's a big difference in my mind between passive asset accumulation and productive capital or risk-taking,' he said.

'This is clearly something the government are looking at closely.

'If I'm accumulating an asset and passively holding that, versus investing in a start-up, a founder-led business or a junior explorer, I think that's quite different.

'I don't think we want to change the incentives around risk, enterprise and innovation.'

Mr Comyn said he planned to discuss the proposed changes with Treasurer Jim Chalmers.

Under the Budget changes, Labor will scrap the current 50 per cent capital gains tax discount and replace it with an inflation-based system designed to tax only 'real' profits above inflation when assets are sold.

Currently, investors who hold an asset for more than 12 months can automatically cut their taxable profit in half before paying tax.

For example, someone who bought shares for $100,000 and later sold them for $200,000 would make a $100,000 profit. Under the current system, they would only pay tax on $50,000 because of the 50 per cent discount.

Under Labor's new model, investors would no longer receive that automatic discount. Instead, the original purchase price would be adjusted for inflation, and tax would only apply to profits above the inflation-adjusted amount.

It will also introduce a minimum 30 per cent tax rate on indexed gains, preventing investors from sharply reducing their tax bill by selling assets during a low-income year.

However, the changes will not apply to small businesses, which are defined as companies with net assets below $6 million or annual turnover of less than $2 million.

The government will also abolish negative gearing for future property investors, although exemptions will remain for newly built homes.

Investment properties that were already negatively geared before Budget night would be grandfathered under the existing rules.

Homeowners who had lived in a property before Budget night would also still be able to negatively gear a property if they later turned it into an investment property.