Interest-only lending is one of the defining structural choices in property investing, and one of the most misused. Done deliberately as part of a strategy, it’s a legitimate tool. Done by default because the repayments look smaller, it’s a trap with a delayed detonation. Here’s the honest picture.
How interest-only actually works
On a standard principal-and-interest (P&I) loan, each repayment covers the interest charged plus a portion of the principal, so the balance shrinks over time.
On an interest-only loan, your repayments cover only the interest for an agreed period, commonly one to five years. The loan balance stays exactly where it started. When the IO period ends, the loan reverts to P&I, and because you now have fewer years left to repay the same principal, repayments jump significantly, often by 30-50%.
That reversion is the single most important thing to understand before choosing IO.
Why investors use interest-only
Three genuine reasons:
- Cash flow. Lower repayments mean the rental income is more likely to cover the property’s costs, reducing the out-of-pocket shortfall. For investors holding multiple properties, this can be the difference between a manageable portfolio and a strained one.
- Tax treatment. Interest on an investment loan is generally tax-deductible; principal repayments are not. IO maximises the deductible component of your repayment while you hold the property. This doesn’t make IO “free”, you’re still paying the interest, but it does mean the repayment is more tax-effective than one that includes non-deductible principal.
- Deploying capital elsewhere. Investors who’d rather direct surplus cash at non-deductible debt (like their own home loan) or the next deposit sometimes use IO on the investment to free up that cash. This connects directly to the offset structure question, where the same deductible/non-deductible logic applies.
The real costs and risks
Now the other side.
You pay more interest overall. Because the balance doesn’t reduce during the IO period, you’re paying interest on the full amount for longer. Over the life of the loan, total interest is meaningfully higher than the P&I equivalent.
You build no equity through repayments. Any equity growth relies entirely on the property’s value rising. If the market is flat, you’re no closer to owning the asset after five years than on day one.
The reversion shock. When the IO period ends, repayments rise sharply. Investors who structured their finances around the lower IO repayment can find the new figure genuinely difficult.
Extension isn’t guaranteed. Many investors plan to simply extend the IO period. Lenders have become more conservative here, particularly on extensions beyond five years, and approval depends on your circumstances at that time, not the assumptions you made at the start.
IO period ending, or weighing whether to use one? A 15-minute strategy call models the reversion, checks your options, and makes sure the structure matches your actual strategy.
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What to do before your IO period ends
If you’re currently on interest-only, start this conversation six months before the period expires. Your options generally are:
- Let it revert to P&I, budgeting for the higher repayment
- Apply to extend the IO period, subject to lender approval and current policy
- Refinance, potentially to another lender with more favourable IO settings
- Restructure, sometimes splitting the loan or adjusting the term is the better answer
Leaving it until the month the reversion hits removes most of these options. Six months’ lead time keeps them all available.
Is interest-only right for you?
It tends to suit investors who: have a clear strategy for the IO period, can comfortably absorb the eventual reversion, are prioritising non-deductible debt reduction elsewhere, and are holding for capital growth with a defined exit or refinance plan.
It tends not to suit investors who: are using IO simply because repayments look smaller, have no plan for the reversion, are relying on being able to extend indefinitely, or would be in difficulty if property values stayed flat.
A useful test: if your IO period ended tomorrow and repayments jumped 40%, what would you do? If you have a clear, funded answer, whether that’s absorbing it, refinancing, or selling on your own terms, then IO is a tool you’re using. If the honest answer is “I’d be in trouble,” then IO is a risk you’re carrying, and the structure deserves a rethink before the reversion date arrives rather than after.
The bottom line
Interest-only is a structural tool, not a discount. It improves cash flow and tax-effectiveness during the IO period, at the cost of higher total interest, no equity accumulation, and a significant repayment increase at reversion. Used deliberately with a plan for the end of the period, it’s sound. Used by default, it creates a problem your future self inherits.
To structure your investment loan properly, book a 15-minute strategy call with Harbir, or explore our investment property loans.
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Or call 02 7245 4001 | Email info@creditstar.com.au
Frequently Asked Questions
Q1. What is an interest-only loan?
Ans. A loan where repayments cover only the interest for a set period (typically 1-5 years), not the principal. The loan balance stays the same during that period.
Q2. Why do investors use interest-only loans?
Ans. For better cash flow (lower repayments), tax effectiveness (investment loan interest is generally deductible while principal isn’t), and to free up capital for non-deductible debt or other purchases.
Q3. Is interest-only cheaper?
Ans. No. Repayments are lower during the IO period, but total interest over the life of the loan is higher because the balance doesn’t reduce during that time.
Q4. What happens when the interest-only period ends?
Ans. The loan reverts to principal and interest, and repayments typically jump 30-50% because the same principal must now be repaid over fewer remaining years.
Q5. Can I extend my interest-only period?
Ans. Sometimes, but it’s not guaranteed. Lenders have become more conservative about extensions, especially beyond five years, and approval depends on your circumstances at that time.
Q6. Is interest-only tax-deductible?
Ans. Interest on an investment loan is generally tax-deductible; principal repayments aren’t. IO maximises the deductible portion of your repayment, though you’re still paying that interest.
Q7. Do I build equity on an interest-only loan?
Ans. Not through repayments, the balance doesn’t reduce. Any equity growth depends entirely on the property increasing in value.
Q8. Can I use interest-only on my home loan?
Ans. Some lenders allow it for owner-occupiers, but it’s more restricted and generally less advantageous, since home loan interest isn’t tax-deductible.
Q9. When should I plan for my IO period ending?
Ans. Start six months before expiry. That preserves all your options: reverting, extending, refinancing, or restructuring. Leaving it late removes most of them.
Q10. Is interest-only a good idea?
Ans. It depends entirely on strategy. It suits investors with a clear plan and capacity to absorb the reversion. It’s risky for anyone choosing it just because repayments look smaller.
This guide is general information only and doesn’t take into account your personal situation, and it isn’t tax or financial advice. Tax treatment depends on your circumstances and can change, consult a registered tax agent. For loan structure advice specific to your circumstances, book a call with Harbir Hundal, Credit Representative 506564 of BLSSA Pty Ltd ACN 117 651 760, Australian Credit Licence 391237.