On 07 Oct 2015 , The Fair Go program that screens on TV3 aired a short documentary about the Unclaimed Funds held by the IRD unclaimed money.  

You can go directly to the IRD at https://www.ird.govt.nz/unclaimedmoney/claiming-unclaimed-money to check to see if your name is on the list.

 This fund mainly consists of bank accounts that have not been active for more than 5 years with a balance of over $100 that are placed in the care of the IRD who have published a list of people and amounts that are recoverable.  

Money stays in the IRD database for no longer than 25 years. If no one claims the money in this time, it is removed from the database and no further claims can be made.

The IRD has now updated the Database in April 2021; so it is more comprehensive and up to date.

This IRD list that was last updated in 2005 contained a list of about $18m owed to various parties.

The Fair Go programm stated that the IRD holds some $136m in unclaimed money, so therefore there are unclaimed funds for $118m is not shown or declared by the IRD.

Note that this money is not earning any interest.

The full Fair go article is available here;

 http://tvnz.co.nz/fair-go/taxman-giveth-video-6398695

The money that the IRD has is mainly from bank accounts that have been idle for longer than 5 years.