The office handles deals which exceed $100 million or which involve sensitive land, including farmland and property fronting the waterfront, rivers or lakes.
It aims to balance the benefits of international investment with protecting the New Zealand estate for current and future generations.
"People who are not New Zealand citizens or who do not ordinarily reside in New Zealand must apply for consent to invest in these assets. That requirement also applies to overseas owned or controlled companies, other incorporated or unincorporated bodies, such as partnerships or joint ventures, and trusts, as well as associates of overseas investors (who may be New Zealanders).
"To be successful, the proposed investment must meet a number of criteria set out in the Overseas Investment Act 2005 (for 'sensitive' land and high value businesses) and the Fisheries Act 1996 (for fishing quota). All decisions to grant or decline consent are published by the OIO," the office says.
The Campaign Against Foreign Control of Aotearoa opposes the approval of such deals, saying these are not in New Zealand's interest.