New Zealand: there is no cap on what a credit card may charge
Most countries in this calculator put a ceiling on consumer credit somewhere. New Zealand does not. The government's own consumer guidance states it plainly: no interest rate limits currently apply, and the law instead governs how interest is calculated and disclosed.
The protections that do exist are aimed somewhere else. New Zealand regulates high-cost consumer credit, defined as an annual rate of 50% or more, and the legislation expressly describes that threshold as higher than a credit card. Those rules are strict, capping total interest and fees at 0.8% of the unpaid balance a day, forbidding anyone from repaying more than twice what they borrowed, and limiting default fees to 30 dollars.
None of it binds a card at around 20%. So the ceiling shown on this page is a modelling bound rather than a legal one, and the discipline has to come from you.
The gap between a mainstream card and a low-rate one is the whole game
Because nothing caps the rate, the spread across the market is wide and permanent. A mainstream purchase rate sits near 20%, while low-rate cards at roughly 13% are widely available from the same banks.
That difference is worth more than almost anything else this calculator can show you. Run your balance at both rates and compare the interest totals: on a balance that takes a few years to clear, switching saves more than a substantial increase in your monthly payment would. The catch is that low-rate cards usually carry an annual fee and no rewards, which is a poor trade when you clear the balance monthly and an excellent one when you do not.
What the rules actually give you
Two things worth knowing about disclosure.
For a revolving credit contract, which is what a credit card is, your lender must give you continuing disclosure every 45 days. That is the statement cycle, and it must be accurate and not misleading.
Responsibility for enforcing all of this changed hands recently: on 1 July 2026 the Financial Markets Authority took over regulation of the Credit Contracts and Consumer Finance Act from the Commerce Commission, following legislation that received Royal Assent on 5 June 2026. Separately, the prescriptive affordability regulations introduced in 2021 were removed on 31 July 2024, though lenders must still assess affordability, ask what the borrowing is for and treat you fairly.
The minimum payment on this page defaults to the greater of about 3% of the balance or a ten dollar floor, which is the common New Zealand convention. Paying it is what makes the interest total on this page as large as it is.