An interest-only mortgage lets you pay just the interest charged on your loan for an agreed period. Your repayments may be lower during that time — but your loan balance is not reducing. The debt stays where it is until principal repayments begin.
This guide is for borrowers who want to understand how interest-only mortgages work in New Zealand, why someone might consider this kind of structure, and what the real trade-offs look like before deciding whether it suits their situation.
Interest-only periods vary by lender, borrower type, loan purpose, and overall application strength. Some borrowers may only qualify for a short interest-only period, while eligible property investors may sometimes be considered for longer terms.
Used in the right circumstances — investment planning, renovations, a temporary change in income, or managing a transition period — interest-only repayments can help with short-term cashflow. But lower repayments now do not necessarily mean paying less overall. Once the interest-only period ends, repayments typically increase because the principal still needs to be repaid over whatever is left of the loan term. That is the part worth understanding clearly before deciding.
With a standard principal-and-interest mortgage, each repayment usually covers two parts: the interest charged by the lender and a portion of the original loan balance.
With an interest-only mortgage, you pay only the interest for an agreed period. During that time:
For example, on a simplified $500,000 loan at 4% interest over 30 years, the monthly principal-and-interest repayment may be around $2,387. If that loan moved to interest-only repayments for two years, the monthly interest payment would be around $1,667 during that period.
That would reduce the monthly repayment by about $720 while the loan is interest-only. However, it is not a true saving unless the wider loan strategy works. The loan balance remains unchanged, and once the interest-only period ends, repayments are usually recalculated over the remaining loan term.
Actual repayments will depend on the loan amount, interest rate, remaining term, lender criteria, and individual circumstances. It is important to run the numbers carefully before deciding whether interest-only repayments suit your situation.
Interest-only mortgages may be considered in different situations, but they are not suitable for everyone. Lenders will still assess affordability, income, credit history, equity, account conduct, and whether there is a realistic plan once the interest-only period ends.
Borrowers who may consider an interest-only structure include:
For property investors specifically, our guide to 10-year interest-only mortgages in NZ explains how longer interest-only periods may work in some investment situations.
First-home buyers may also wonder about interest-only repayments, but lenders usually assess affordability, deposit or equity position, loan purpose, and long-term repayment ability carefully before approving this type of structure.
The main risk is that the loan balance does not reduce during the interest-only period. That means:
This is why interest-only should be reviewed as part of the wider mortgage plan, not treated as a simple way to make repayments lower.
If you’re using an interest-only mortgage to invest, renovate, manage cashflow, or get through a transition period, having a clear plan for what happens once the interest-only term ends is just as important as the structure itself.
That plan might include:
One issue we often see is borrowers benefiting from an interest-only period without fully thinking through what comes next — and that is where the structure can start to create pressure rather than relieve it. Interest-only should never be treated as a pause button with no follow-up plan. Because the principal is not reducing during that period, the next stage of the loan needs to be clearly understood before you lean on lower repayments now.
One of the most important things to understand with an interest-only mortgage is what happens when the interest-only period comes to an end.
Because the principal is not reducing during that time, when the loan switches back to principal-and-interest repayments, the remaining balance still needs to be repaid — but now over a shorter remaining term. That is where the repayment increase comes from, and it is worth understanding before you commit to the structure.
Here is a simplified example to show how it can play out:
Before switching to interest-only, the principal-and-interest repayment would be around $2,387 per month.
During the two-year interest-only period, that drops to around $1,667 per month — a lower repayment in the short term.
But when the interest-only period ends, the loan now needs to be repaid over the remaining 28 years rather than the original 30. Because the principal has not moved during that time, the new principal-and-interest repayment may rise to around $2,476 per month, depending on the loan terms and interest rate at that point.
That is the trade-off — interest-only can create breathing room when you need it, but it can also mean higher repayments waiting on the other side if there is no clear plan for what comes next.
Interest-only can be useful in the right situation, but it should be reviewed carefully before applying. Lower repayments during the interest-only period can help with cashflow, but the loan balance is not reducing and repayments may increase once the interest-only term ends.
At Platinum Mortgages, we can help you look at whether an interest-only structure fits your goals, income, loan term, equity position, and longer-term repayment plan. We can also help compare it with other mortgage structures, such as principal-and-interest repayments, split loans, or refinancing your mortgage where appropriate.
If you are unsure whether interest-only is right for your situation, it may help to speak with a mortgage adviser before making a decision.
Angela is an accredited Financial Adviser, licensed under FSP742251 and has been in the Financial Industry since 2006. Our 5-star Google reviews reflect the excellent customer experience we promise — making your home loan journey positive, stress-free, and rewarding. At Platinum Mortgages, our clients are the reason we exist — so you can be confident every step is guided by genuine care and expertise.
