INZ Operational Manual: Temporary Entry, E4.5.5, F.2.20
If your partner is a New Zealand citizen, or has a NZ Residence or Temporary Visa (or is applying for one), you can apply for a Temporary Visa on the basis of your partnership with them. You’ll need to provide evidence to Immigration New Zealand that the two of you are in a genuine and stable relationship. They’ll take into account factors like how long you’ve been together, whether you live together, and how financially dependent on each other you are.
The strongest evidence you can give Immigration NZ will be “hard” evidence like financial statements or other documents that have both your names on them – like a joint mortgage or bank account statement, a joint tenancy agreement or electricity bill, or your child’s birth certificate with the two of you recorded as the parents. “Soft” evidence that you’re in a relationship – like letters between you or photos of you together – will help support your case but won’t be enough on its own.
If your partner has New Zealand residence or citizenship, and the two of you have been living together for at least 12 months, you may also qualify for residence: for more details see “Requirements for Family residence categories” under “Residence Class Visas: Living in New Zealand permanently”.