A New Zealand mortgage is a home loan under New Zealand rules, and while the repayment maths is the same everywhere, the products, the rate structures, and the traps are local. Most borrowers fix for one to five years, or float, or split the loan between fixed and floating. Revolving credit and offset accounts let savings reduce interest. Terms usually run to 25 or 30 years. This guide explains the structures, the repayment formula with the page default figures, the fortnightly trap, and the extra-payment arithmetic, all in New Zealand dollars and without quoting a live rate, because rates move and this guide should not date.

Fixed, floating, revolving, and offset

A fixed rate locks the interest rate for a chosen term, commonly six months to five years, and the repayment is fixed for that term. Certainty is the benefit: the payment cannot rise while fixed, which makes budgeting straightforward. The cost is inflexibility: breaking a fixed term early usually incurs a break fee, and extra repayments may be limited during the fixed period.

A floating rate moves with the market and with the Reserve Bank official cash rate, and the repayment can rise or fall. Flexibility is the benefit: extra repayments and lump sums are usually free, and the loan can be repaid or restructured without a break fee. The risk is the payment rising, which is why floating suits borrowers who can absorb movement or who plan to repay quickly.

Splitting the loan, part fixed and part floating, hedges both ways: the fixed portion gives certainty on part of the payment, and the floating portion gives flexibility for extra repayments. Revolving credit is a floating overdraft-style facility secured against the home: the balance fluctuates as money moves in and out, and interest is charged on the daily balance. Offset accounts link savings to the loan so that the savings balance reduces the interest-bearing balance, without the money leaving your control.

The repayment formula, on the default loan

Each period, interest is charged on the balance at the period rate, the yearly rate divided by the number of payments a year. At 6.5 percent a year paid monthly, the period rate is 0.5417 percent a month. The repayment is set by the standard loan formula so that the same payment, part interest and part principal, clears the balance exactly at the end of the term.

On the page default loan, the monthly repayment is NZ$3,792.41, and NZ$3,250.00 of the first payment is interest, leaving only NZ$542.41 of principal. That front-loading is normal: early payments are mostly interest because the balance is largest. As the balance falls, the interest share falls and the principal share grows, until the last payments are almost entirely principal.

The yearly picture makes the cost vivid. Over a 30-year term, the total interest on a loan of this size runs into hundreds of thousands of dollars, which is why term and extra payments matter more than small rate differences. Shortening the term raises the payment but cuts total interest sharply, and the calculator shows both figures for any term you enter.

The fortnightly trap: 26 halves are 13 wholes

A true fortnightly repayment takes the monthly payment, halves it, and pays that half every two weeks. There are 26 fortnights in a year, so 26 half-payments equal 13 monthly payments, not 12. That thirteenth payment is the entire saving mechanism: it is an extra monthly payment every year, applied to principal, which shortens the term and cuts interest.

On the default loan, the fortnightly payment is NZ$1,749.52 against NZ$3,792.41 a month, and the total interest is NZ$764,623.58 against NZ$765,266.93 monthly. The difference from timing alone is small, about NZ$643, because the calculator fortnightly figure here spreads the same annual total differently. The large savings attributed to fortnightly payments come from the thirteenth payment, not from the frequency, and a monthly payer who makes one extra payment a year gets the same benefit.

The trap is paying fortnightly without the extra payment: some lenders simply divide the monthly payment by two and collect it fortnightly over the same term, which changes nothing except the payment dates. Check whether your fortnightly schedule actually delivers 26 half-payments a year, or merely reschedules 12 monthly payments.

Extra payments: NZ$200 a month, four years, NZ$121,989.57

Extra payments attack principal directly, and because interest is charged on the balance, every extra dollar saves interest on every remaining payment. On the default loan, adding NZ$200 a month shortens the term by about four years and saves NZ$121,989.57 in interest, according to the page figures. The arithmetic is the same mechanism as the fortnightly thirteenth payment, only larger.

The best extra payment is the one that survives the fixed term. During a fixed period, extra repayments may be capped or incur a break fee, so the time to add lump sums is at refixing, or into the floating portion of a split loan, or into an offset account where the money stays accessible. A lump sum at refixing has the same effect as years of small extras, because it cuts the balance that all future interest is charged on.

Offset and revolving facilities deserve a second look here. Money held in offset reduces the interest-bearing balance while remaining available, which is the flexible version of an extra payment: it saves interest without locking the money away. For borrowers with irregular income, offset often beats a fixed extra payment, because the money can be withdrawn when needed.

Deposit, loan size, and the rate you should enter

Deposit size sets the loan-to-value ratio, LVR, which is the loan divided by the property value. A 20 percent deposit gives an 80 percent LVR, and loans above 80 percent LVR are low-deposit lending, which banks limit as a share of their new lending under Reserve Bank restrictions, and which usually carries a low-equity margin or fee. A larger deposit therefore buys not only a smaller loan but often a better rate and fewer restrictions.

The rate you enter in the calculator should be the rate you will actually pay, including any low-equity margin, not the advertised headline rate. Advertised rates assume a strong deposit and clean servicing, and the rate offered to a low-deposit borrower can be materially higher. Enter the offered rate, not the advertised one, and the repayment figure will match the bank letter.

Serviceability is the other gate: banks test whether you can afford the loan at a rate higher than the actual rate, to allow for rate rises. A loan that fits at 6.5 percent may not pass a serviceability test at 8 or 9 percent, and that test, not the repayment figure, is what decides approval. The calculator shows affordability; the bank applies the buffer.

Refixing and refinancing: the five-year balance

At the end of a fixed term, the loan refixes: you choose a new term, or float, or restructure, and the balance at that point is the starting point for the next decision. The page shows the five-year balance for the default loan, which is the figure to carry into refixing negotiations. Knowing it in advance prevents the common surprise of a balance barely moved after five years of payments, because early payments are mostly interest.

Refinancing, moving lender, is worth testing at every refix, because rates, cash contributions, and fee structures differ, and loyalty is rarely rewarded with the best rate. The costs are legal fees, possible break fees if a fixed term is broken early, and valuation, and the benefit is the rate difference over the remaining term. The calculator refinancing comparison runs those numbers, but the decision should include the serviceability test at the new lender too.

Frequently Asked Questions

How is an NZ mortgage repayment worked out?

Each period, interest is charged on the balance at the period rate, the yearly rate divided by payments a year, and the repayment is set so the same payment clears the balance exactly at the end of the term. Early payments are mostly interest.

Is paying fortnightly always cheaper than paying monthly?

Only if it delivers 26 half-payments a year, which is 13 monthly payments. The extra payment is what saves interest. A fortnightly schedule that merely reschedules 12 monthly payments saves nothing.

What is a low-deposit loan in New Zealand?

A loan above 80 percent loan-to-value, meaning a deposit below 20 percent. Banks limit low-deposit lending as a share of new loans under Reserve Bank restrictions, and it usually carries a low-equity margin or fee.

Should I fix or float my NZ mortgage?

Fixing gives payment certainty for the term but limits extra repayments and can incur break fees. Floating gives flexibility for extra repayments and restructuring but exposes the payment to rate rises. Splitting the loan hedges both ways.

How much does NZ$200 extra a month save?

On the page default loan, about four years off the term and NZ$121,989.57 in interest saved. Extra payments cut the balance that all future interest is charged on.

What rate should I enter in the calculator?

The rate you will actually pay, including any low-equity margin, not the advertised headline rate. The offered rate is what determines the repayment in the bank letter.