Is a capital gains tax a hill worth dying on?

Both are also political promises which have implications for whether the tax is, indeed, fair.

Is it fair that I enjoy whatever capital gains I receive from my home, tax free, while my friends are taxed on savings to raise a deposit for a home?

Whatever is promised by the Tax Working Group report will leave Labour in an invidious position. Capital gains taxes are inherently complicated and New Zealand’s existing tax system is designed around not having one in place.

The best way to implement one would be to develop it slowly and rigorously, with little political input, to minimise unintended consequences.

But though the Government might prefer not to talk about how a tax would work in practice, National will force it to. During the election campaign in 2017, Labour was constantly on the back foot amid an intense campaign by National’s ‘‘let’s tax this’’ attack advertising.

Jacinda Ardern was eventually forced to rule out major changes before the 2020 election, but, according to pollsters, the damage was done.

Unless Ardern and Finance Minister Grant Robertson are ready to make the case continually for whatever changes are proposed, the Government’s proposed CGT will be whatever National says it is.

Pressure for exemptions from any changes to the existing regime on gains, beyond what have already been announced, will be intense. Although further exemptions will only undermine the efficiency and revenue of the tax, the horse-trading of coalition politics makes it almost inevitable.

So far NZ First has remained silent on its policy on a CGT, but if Winston Peters can be convinced to support it at all he is certainly unlikely to do so without extracting some tangible win for the party to promote to his supporters.

A refusal to grant an exemption for baches will certainly upset wealthy New Zealanders, who were unlikely to vote Labour anyway, but also thousands of cashed-up bogans and others who certainly might.

All of this comes amid high uncertainty about what a CGT would raise in the coming decade, in an environment where low interest rates have pushed asset valuations to levels that may not be sustainable, especially if the economy slows.

For all its belief that there is a major problem in the tax system which could be fixed through a change in mindset, it is likely to be dawning that the tax will be politically challenging unless major changes are made, which will undermine how much is raised as well as how much ‘‘fairer’’ the tax system will become.

It will also be so easy for its opponents to demonise that the Government must wonder whether the risk of trying is worth it.