In a residential building, you can generally fit a dishwasher without building consent as long as it discharges to an existing sanitary drainage trap.
Certain other flood/overflow protection provisions may be required if it is a multi-unit building, or if it is a commercial unit that requires you to fit a backflow prevention device.
Visit the Building Performance website for everything you need to know before you start building work that is exempt from the building consent process, including who you should engage to do the work, what rules to follow and where to go to for advice: Building work that doesn't need a building consent