Resource Management Act 1991, s 326
You have the right to do normal things in your home, including have parties.
If a neighbour thinks you’re making too much noise, they can complain to the Environmental Health section of their local council. An enforcement officer will usually come and investigate.
In practice, whether an enforcement officer thinks the noise is “excessive” (too much) might depend on the time of day. You can usually have normal party noise in the evening but after 10pm or 11pm (depending on your local council’s policy) you should turn the music right down.
Some practical advice: get to know your neighbours, and be friendly. People are much less likely to complain if they know and like you. Also, if you know your neighbours have young children, or someone who’s ill, or other particular needs for peace and quiet, you might be able to think of ways to avoid being too noisy or find a compromise that works for everyone.
Note: Excessive noise is “noise under human control and of such a nature as to unreasonably interfere with the peace, comfort, and convenience of any person (other than a person in, or at, the place from which the noise is being emitted)”. But it doesn’t include noise from aircrafts, vehicles on the road, or trains.