A project to gather information on what wealthy people own could be used by a future government

Inland Revenue's started writing to 400 New Zealanders with a net worth of at least 20 million dollars, asking about their assets.

It's part of the High-Wealth Individuals Research Project, aimed at figuring out how much the ultra wealthy pay in tax, as a share of their economic wealth.

PWC partner Geof Nightingale says it won't change policy with this government because the Prime Minister's made some clear commitments.

But he says a future administration could use it to decide on tax design policy.