Overhang seats explained: why Parliament can have more than 120 MPs

New Zealand's Parliament normally has 120 seats. But after the 2023 election it had 122, and after a by-election, 123. The reason is overhang, one of the quirks of MMP. It can move the majority line on election night, so it's worth understanding.

How overhang happens

Under MMP, the 120 seats are first shared out by party vote. Each party's electorate wins are counted inside its share, and list seats fill the rest. See how MMP works.

Usually a party wins fewer electorates than its total entitlement, so it gets list seats to make up the difference. But sometimes a party wins more electorates than its party vote justifies. It can't be given negative list seats, and electorate winners can't be unseated, so:

1. the party keeps all its electorate seats,
2. the other parties keep the seats their party vote entitles them to, and
3. Parliament gets bigger by the number of extra seats.

Every overhang under MMP

There was no overhang in 1996, 1999, 2002, 2017 or 2020, so Parliament had exactly 120 seats after those elections. Overhang usually comes from parties that win electorates on strong local or Māori electorate support but have a smaller nationwide party vote.

The 2023 overhang, step by step

1. Te Pāti Māori won 3.1% of the party vote, enough for about four seats.
2. It won six of the seven Māori electorates.
3. It kept all six, creating two overhang seats.
4. Parliament had 122 seats, and a majority became 62.
5. In the Port Waikato electorate, a candidate's death meant the electorate vote was held later, in a by-election on 25 November 2023. National won it. Because the party vote seats had already been allocated, the by-election winner was an extra MP, taking Parliament to 123.

Why overhang matters on election night

• The majority line moves. If there's one overhang seat, a majority is 61 of 121. With two, it's 62 of 122.
• Results can shift. Overhang depends on electorate results, and close electorates can change with special votes. In 2023, Te Pāti Māori had four seats on election night and six in the official result.
• Bloc arithmetic changes. A party's overhang seats count for whichever bloc it supports.

Is overhang fair?

Views differ:

• For keeping it: electorate MPs are directly elected and shouldn't be removed, and overhang is rare and small.
• Against it: it gives a party more seats than its party vote, so Parliament is less proportional than it should be.
• Reviews: both the Electoral Commission's 2012 MMP review and the Independent Electoral Review in 2023 recommended removing overhang seats, but the law hasn't changed. The rules for 2026 are the same as in 2023.

Questions and answers

Sources

• Electoral Commission: overhang rules and 2023 official result.
• Te Ara: parties in Parliament 1999–2023.
• 2023 New Zealand general election: Port Waikato by-election and overhang.

This guide is general information about New Zealand elections, checked against the sources linked above on 3 November 2026. For anything about your own enrolment or vote, check vote.nz or call the Electoral Commission on 0800 36 76 56.