The New Zealand parliamentary electoral system has been based on the principle of mixed-member proportional (MMP) since the 1996 election. MMP was introduced following a referendum in 1993. It replaced the first-past-the-post (FPP) system New Zealand had previously used for most of its history. Under the MMP system, New Zealanders have two secret ballot votes to elect members of Parliament (MPs). The first vote is for a candidate from an electorate, a geographic electoral district. The second is the party vote for the political party the voter wants to form the government.

The timing of elections is governed by the Constitution Act 1986 and political conventions. Generally, parliamentary general elections are held approximately every three years and are conducted by the independent Electoral Commission.

New Zealand's Parliament has a single house, the House of Representatives, usually with 120 MPs, although the number can increase due to a small number of overhang seats, depending on the outcome of the electoral process. The total number of MPs a party has in a term of parliament is in principle determined by its share of the party vote. The 54th Parliament, elected in 2023, comprises 123 seats: 72 were filled by electorate MPs and the remaining seats filled by list MPs selected from ranked party lists.

In 1893, New Zealand was the first self-governing country to grant women the right to vote. This meant that, theoretically, New Zealand had universal suffrage from 1893, meaning all adults 21 years of age and older were allowed to vote (in 1969 the voting age was lowered from 21 to 20. It was lowered further to 18 in 1974). However, the voting rules that applied to the European settlers did not apply to Māori, and their situation is still unique in that seven seats in Parliament are elected by Māori voters alone.

In contemporary New Zealand, generally all permanent residents and citizens aged 18 or older are eligible to vote. The main exceptions include citizens who have lived overseas continuously for too long, and convicted persons who are detained in a psychiatric hospital or serving a prison term of more than three years.

Term of parliament

Although parliamentary elections are held at least every three years, this has not always been the case. In New Zealand's early colonial history, the parliamentary term could last up to five years – as established by the New Zealand Constitution Act 1852. The term was reduced to three years in 1879 because of concerns about the growing power of central government.

Since then, the term has been altered three times. During the First World War it was extended to five years. In the early 1930s, during the Great Depression, it was pushed out to four years. This proved to be unpopular with the electorate and after the election of 1935, the term was reduced to three years again. It was extended to four years once again during the Second World War, but returned to three years afterwards. In 1956, the term of three years was 'entrenched' in the Electoral Act which means that it can only be changed by achieving a majority in a national referendum or by a vote of 75% of all members of Parliament.

In 2013 the Government established an advisory panel to conduct a review of constitutional issues – including an examination of the term of parliament. Other issues discussed at public meetings held by the panel were the number of MPs New Zealand should have, whether a written constitution is needed, and whether all legislation should be consistent with the Bill of Rights Act. Both Prime Minister John Key and Opposition leader David Shearer expressed support for an extension of the parliamentary term to four years. The main argument put forward in support of a longer term is that "Governments need time to establish and then implement new policies".

In the 1967 New Zealand parliamentary term referendum, and nearly 70 of the votes were also opposed to extending the term. The 1990 New Zealand parliamentary term referendum also found nearly 70% of the voters were opposed to extending the term.

In 2013, an opinion poll on the news website Stuff found that of 3,882 respondents, 61% were in favour of changing to a four-year term.

A 2020 poll found that 61% of respondents supported changing to a four-year term and 25% were against it. The rest were undecided.

Māori seats

A unique feature of New Zealand's electoral system is that a number of seats in Parliament are reserved exclusively for Māori. However, this was not always the case. In the early colonial era, Māori could not vote in elections unless they owned land as individuals. European colonists were quite happy with this state of affairs because, according to NZ History online, "they did not think Māori were yet 'civilised' enough to exercise such an important responsibility". At the time, Māori were dealing directly with the Crown in regard to the Treaty of Waitangi and had little interest in the 'pākehā parliament'.

During the wars of the 1860s, some settlers began to realise it was necessary to bring Māori into the British system if the two sides were to get along. After much debate, in 1867 Parliament passed the Maori Representation Act, which established four electorates solely for Māori. The four Māori seats were a very minor concession; the settlers had 72 seats at the time and, on a per capita basis, Māori should have got up to 16 seats. All Māori men (but not women) over the age of 21 were given the right to vote and to stand for Parliament.

Full-blooded Māori had to vote in the Māori seats and only Māori with mixed parentage ('half-castes') were allowed to choose whether they voted in European electorates or Māori electorates. Some voters having the choice between the two voting systems (settler seats versus Māori seats) continued until 1975.

From time to time there was public discussion about whether New Zealand still needed separate representation for Māori – which some politicians described as a form of apartheid. Māori were only allowed to stand for election in European seats (or general electorates) from 1967.

In 1985, a Royal Commission on the Electoral System was established. It concluded that "separate seats had not helped Maori and that they would achieve better representation through a proportional party-list system". The commission recommended that if a mixed-member proportional (MMP) system was adopted, the Māori seats should be abolished. However, most Māori wanted to keep them and the seats were not only retained under MMP, their "number would now increase or decrease according to the results (population numbers) of the regular Māori electoral option". As a result, in 1996 before the first MMP election, the number of Māori seats increased to five – the first increase in 129 years. In 2002, it went up to seven.

Developments in voting rights and eligibility

Secret ballot In European seats, the secret ballot was introduced in 1870. However, Māori continued to use a verbal system – whereby electors had to tell the polling official which candidate they wanted to vote for. Māori were not allowed a secret ballot until 1938 and even voted on a different day. According to NZ History online: "Up until 1951 voted on a different day from Europeans, often several weeks later." It was not until 1951 that voting in the four Māori electorates was held on the same day as voting in the general election.

NZ History also states: "There were also no electoral rolls for the seats. Electoral officials had always argued that it would be too difficult to register voters (supposedly because of difficulties with language, literacy and proof of identity). Despite frequent allegations of electoral irregularities in the Maori seats, rolls were not used until the 1949 election."

Today, voters cast their secret ballot at voting places or via postal vote. Special votes are cast by electors whose names are not on the printed electoral rolls held in that voting place (for example, if they were voting outside of their normal electorate, their enrolment had lapsed because they had moved without updating their details, or they were on the unpublished roll).

Māori representation Māori representation by four Māori members was introduced in 1868, see First Māori elections. Most Māori land was held collectively, so most Māori did not meet the property qualification for voting.

Universal male suffrage Universal manhood suffrage was introduced in the 1881 New Zealand general election, following a law change in 1879. Previously there had been a property qualification for voting, and this was often listed in earlier electoral rolls.

Special electorates for gold miners in the South Island for which the only qualification was holding a mining licence, the Gold Fields electorate and the Gold Field Towns electorate took part in the 1866. They existed between 1862 and 1870.

Women's suffrage

In early colonial New Zealand, as in most Western countries, women were totally excluded from political affairs. Led by Kate Sheppard, a women's suffrage movement began in New Zealand in the late 19th century, and the legislative council finally passed a bill allowing women to vote in 1893.The right to vote, New Zealand History Online This made New Zealand the first country in the world to give women the vote. However, they were not allowed to stand as candidates until 1919, and the first female Member of Parliament (Elizabeth McCombs) was not elected until 1933 – 40 years later. Although there have been three female prime ministers (Jenny Shipley, Helen Clark and Jacinda Ardern), women remain somewhat under-represented in Parliament. Following the election in 2011, 39 MPs (almost one third) were women. After the 2011 election, on a global ranking New Zealand is 21st in terms of its representation of women in Parliament.

Prisoners' right to vote

The voting rights of prisoners in New Zealand have been in a near constant state of flux since the earliest elections – currently prisoners serving terms longer than three years cannot vote.

In 2010, the National government passed the Electoral (Disqualification of Convicted Prisoners) Amendment Bill which removed the right of all sentenced prisoners to vote (regardless of the length of sentence imposed). The Attorney-General stated that the new law was inconsistent with the Bill of Rights Act, which says that "every New Zealand citizen who is over the age of 18 years has the right to vote and stand in genuine periodic elections of members of the House of Representatives".Prisoners and the Right to Vote, NZ Council for Civil Liberties The Electoral Disqualification Bill was also opposed by the Law Society and the Human Rights Commission who pointed out that, in addition to being inconsistent with the Bill of Rights, the legislation was also incompatible with various international treaties that New Zealand is party to.

Law Society Human Rights committee member Jonathan Temm, in a written submission, told Parliament's law and order committee that: "It is critical for the function of our democracy that we do not interfere with the right to vote." With specific reference to decisions made by courts in Canada, Australia and South Africa, and by the European Court of Human Rights in respect of the United Kingdom, he pointed out that "every comparable overseas jurisdiction has had a blanket ban (against prisoners' voting) struck down in the last 10 years".

In 2020, the Electoral Act was amended so that only persons serving a sentence of imprisonment for a term of three years or more are disenfranchised – this restores the law to the position prior to 2010.

Election day