RBNZ says the decision has no implications for monetary policy.
IAG is New Zealand's largest general insurer with about 45% of the market and owns the NZI, AMI, State and Lumley brands.
Insurance Australia Group is preparing a disclosure about collapsed financier Greensill after fund manager Bronte Capital raised questions about IAG's exposure.
Ethical Kiwisaver funds are being directed into low-cost housing under Community Finance, an impact investment platform.