The company was created in 1 April 1987 as a State-Owned Enterprise from the corporatisation of the New Zealand Post Office, a government department, following the recommendations of the 1986 Mason-Morris Review. The other state-owned enterprises formed from the New Zealand Post Office: the erstwhile monopoly telephone operator (Telecom Corporation of New Zealand Limited), and a savings bank (Post Office Bank Limited), were later privatised. The majority owners were, respectively, two United States Baby Bells and an Australian bank.
New Zealand Post began its life with 1,244 post offices, later rebranded as PostShops. Of these 906 full post offices and 338 postal agencies, 600 post offices or bank branches were downsized or closed after government subsidies expired in February 1988. As of March 1998, there are 297 PostShops, and 705 Post Centres. However, there were now more outlets than before corporatisation, with 2945 other retailers of postage stamps. There has been a reduction in the 'real' price of postage, with the last nominal drop of the postage rate from NZD0.45 to NZD0.40 in 1996.
The Lange government's Postal Services Act 1987 also reduced the monopoly of New Zealand Post to a limit of NZD1.75 and 500g. It was gradually reduced to NZD0.80 in December 1991 until the 1998 legislation took effect.
The Postal Services Act 1998, passed by a National-New Zealand First coalition government, repealed the 1987 Act. The new law provides for any person to become a registered postal operator by applying to the Ministry of Economic Development. Registration as a postal operator is compulsory for letters with postage less than NZD0.80.
New Zealand Post's exclusive right to be the 'sole operator' under the Act for the purposes of the Universal Postal Union expired on 1 April 2003. For practical purposes, this meant another postal operator could theoretically issue stamps identified simply as 'New Zealand' with UPU membership. At around the same time, it adopted an fern-shaped identifying mark on its postage stamps, to be used on the majority of its future issues.
In 2002, New Zealand Post, as part of government policy, opened the bank Kiwibank Limited in the majority of its PostShop and Books & More post office branches.
New Zealand Post also runs the Electoral Enrolment Centre as a 'business unit' under contract to the Minister of Justice. Its function is to compile and maintain all parliamentary electoral rolls.