The Government has once again said it is not considering a wealth, death, or inheritance tax - despite speculation from Opposition parties it is "preparing" for it.

An inheritance tax is imposed on people who are bequeathed or get assets from the estate of someone who's died, also referred to as a death tax.

A wealth tax is levied on assets owned by a taxpayer and can apply to a range of types, including cash, bank deposits, shares, fixed assets, personal cars, real property, pension plans, money funds, owner-occupied housing, and trusts.

An Official Information Act request sent to Minister for Revenue David Parker in May asked if he'd considered a wealth or inheritance tax at any point, but he refused the request because that information doesn't exist.

But recently, Opposition party leaders have speculated that a wealth, death, or inheritance tax could be on the horizon.

This is because in Budget 2021, $5 million was secured for the next two years for Inland Revenue and Treasury to research the level of tax high-wealth New Zealanders are paying.

ACT Party leader David Seymour said on Sunday the Government is "clearly gearing up for an inheritance tax" as a result of this funding and is "preparing another tax grab". 

"A better way to fight inequality would be if kids were going to school and infrastructure was being built so there is opportunity," he said.

"Instead, we have a Government more interested in redistributing wealth than allowing the opportunities to create it."

National Party leader Judith Collins also believes an inheritance tax could be on the way, tweeting on Monday: "Mark my words... Jacinda Ardern once ruled out a death tax. Expect a 'softening up' for Kiwis to get a death tax."

The Prime Minister said on the election campaign trail in 2017 an inheritance tax wasn't an option for a Labour-led Government.

A spokesperson for Parker told Newshub a wealth, death, or inheritance tax is still "not being considered". They also pointed to Labour's 2020 manifesto that says other than the 39 percent tax rate for income over $180,000, there would be no major tax changes under this Government.

In early June, Parker appeared before Parliament's Finance and Expenditure Committee to answer questions about his portfolio's wins in Budget 2021.

Green MP Chlöe Swarbrick quizzed him on Inland Revenue's research and asked what he would do if it's found the wealthiest aren't paying their "fair share" of tax.

"Perhaps nothing," he said. "It just gives us an information base on which to base future decisions."

He again reiterated there won't be any new taxes this term, other than the new 39 percent tax rate for income over $180,000.

National Party MP Nicola Willis asked him whether there's anything more than just a research unit that will give Parker the database to later campaign for a wealth, inheritance, or death tax at the next election.

"I'm not planning a wealth, inheritance, or death tax, and I'm not seeking advice from my ministry on those issues, so the answer to those questions is it isn't any of those things," he said.

The Green Party has previously called for a wealth tax for those whose net wealth is over $1 million. They estimate this would be about 6 percent of New Zealanders who would be required to pay 1 percent tax on assets over the $1 million threshold. Their policy didn't include mortgages or other debts.