An anticipated report by the IRD could put a capital gains tax back on the agenda.

The report is due to be released Wednesday, and it will look into 400 of New Zealand's wealthiest families and individuals.

Speculation indicates this report could pave the way for New Zealand to establish a capital gains tax, aided by Jacinda Ardern's absence.

University of Auckland Taxation Law Professor Craig Elliffe says in the long term, there needs to be some form of tax on capital gains.

"The simple demographic equation is one that says you either have to increase GST by another click (and it's already quite high) or you have to increase income taxes amongst a smaller group of people that are paying those taxes. That gets to very high levels, which is not very fair on labour income."

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