Disclaimer:
This article provides general information only and does not constitute financial, legal, tax, or investment advice. Property investment involves risk. Always do your own research and seek personalised advice from qualified professionals before making investment decisions.
Key Takeaways
- Interest-only loans reduce your monthly payments by not requiring principal repayment during the interest-only period.
- They can improve cash flow but you are not building equity through repayments.
- Available interest-only periods depend on the lender, product, application and approval at the time.
- Whether an interest-only loan is suitable depends on the borrower’s circumstances, total cost, risks and plan for principal repayment.
- Consider the impact on your long-term wealth building and retirement timeline.
Interest-only loans are one repayment structure used for some property lending. Understanding the lower initial payment, unchanged principal and later repayment risk helps borrowers compare them with principal-and-interest lending.
When you take out an interest-only loan, your monthly repayments cover only the interest charged on the loan, not the principal. This means lower payments compared to a principal and interest loan, but your loan balance stays the same throughout the interest-only period.
How Interest-Only Loans Work
With a standard principal and interest loan, each payment reduces your loan balance over time. With an interest-only loan, you are essentially renting money from the bank. You pay for the privilege of using their money, but you are not paying it back.
Example Comparison (on a $500,000 loan at 6.5%):
- Illustrative interest-only payment: about $2,708 per month
- Illustrative principal and interest payment over 30 years: about $3,160 per month
- Illustrative initial monthly payment difference: about $452
- Illustrative initial annual payment difference: about $5,424; this is not an overall saving
The initial payment difference must be weighed against the unchanged principal, later repayments, rate changes, fees and total interest cost.
The Benefits of Interest-Only Loans
Improved Cash Flow
The most obvious benefit is reduced monthly payments. For investment properties, this can mean the difference between positive and negative cash flow, or simply having more buffer for unexpected expenses.
Tax Efficiency
From 1 April 2025 Inland Revenue allows 100% of interest incurred to be claimed only where the interest is not private and the general deductibility rules are met. Loan purpose, tracing, ownership and use can affect the result, so do not choose a repayment structure solely for an assumed tax outcome.
Flexibility for Portfolio Growth
The lower initial payment leaves cash available for other purposes, but using it for another deposit, renovations or reserves changes the borrower’s risk and must fit their budget and lending position.
The Drawbacks and Risks
No Equity Build-Up Through Repayments
The biggest downside is that you are not reducing your loan balance. During the interest-only period the loan does not build equity through scheduled principal repayments; equity can still change if the property value or loan balance changes for other reasons. If property values fall or stagnate, you could find yourself in a difficult position.
Higher Payments Eventually
When the interest-only period ends, your payments will jump significantly because you need to repay the full principal over a shorter remaining term. A $500,000 loan that was interest-only for 5 years will need to be repaid over 25 years instead of 30, meaning higher monthly payments.
Payment Shock Example:
In this simplified constant-rate example, the payment rises from about $2,708 a month to about $3,406 when principal is repaid over the remaining 25 years. The actual later payment depends on the balance, rate, remaining term, fees and lender terms.
Lending Restrictions
Lenders apply their current affordability, credit and policy assessments to an interest-only application. Available amounts, interest-only periods and extensions are lender- and application-specific and are not guaranteed.
When Interest-Only Makes Sense
Questions to Assess Before Choosing Interest-Only:
- ☐ Compare the tax treatment of each loan purpose; do not assume deductibility
- ☐ Test whether lower initial payments justify the added debt and total cost
- ☐ Test repayments at the end of the interest-only period and at different rates
- ☐ Record how and when principal repayment is expected to begin
- ☐ Check the written term, fees, restrictions and approval conditions
Risk Questions:
- ☐ Is there no workable plan for the later principal-and-interest payment?
- ☐ Would the structure leave debt beyond the intended repayment timeline?
- ☐ Does affordability depend on the temporary lower payment?
- ☐ Has the use of the initial cash-flow difference been budgeted?
Strategies for Using Interest-Only Effectively
Debt Recycling
Using different repayment structures across home and investment lending can change total interest, tax treatment, flexibility and risk. Have the loan-purpose tracing and personal tax consequences checked before changing debt or repayments.
Offset Accounts
Some investors maintain an offset account against their interest-only loan. The cash in the offset reduces the interest charged, but remains accessible. This gives you the benefits of interest-only while still having funds working to reduce your interest costs.
Regular Reviews
Review the arrangement before the interest-only period ends and when rates, income, expenses, property plans or loan terms materially change. Compare the current repayment, total cost and principal-repayment plan.
Talking to Your Lender
For a new or renewed interest-only period, ask the lender what information, affordability assessment and repayment plan it requires. Requirements and approval depend on the lender and application.
Changing repayment structure depends on the lender, contract, a fresh assessment and any fees or restrictions. If using a mortgage adviser, check their regulated status, service scope, lender panel, fees and commission before relying on advice.
The Bottom Line
Interest-only loans are a tool, not a strategy in themselves. They can lower initial payments, but do not reduce principal through scheduled repayments and can increase total cost and later repayment pressure. Tax treatment and portfolio outcomes are not guaranteed.
The key is having a clear plan: know why you are using interest-only, how long you will use it, and what you will do when the interest-only period ends. Suitability should be assessed against the written offer, budget, total cost, repayment plan and the borrower’s circumstances.