Only if you are carrying NZ$10,000 or more in cash, or the equivalent in another currency, including travellers' cheques and similar. Then you must complete a Border Cash Report, either online within 72 hours before you travel or on the form a Customs officer gives you before passport control. There is no fee and no limit on how much you may bring: the report exists to detect money laundering. Not reporting cash over the threshold is an offence, and the cash can be seized. Source: New Zealand Customs Service — https://www.customs.govt.nz/travel-to-and-from-new-zealand/border-cash-report