Interest-only (IO) loans allow borrowers to pay only the interest component of a mortgage for a set period — typically 1–5 years — without reducing the principal. They are popular among Australian property investors as a cash flow management tool and to maximise the deductible portion of loan repayments.
How Interest-Only Loans Work
In a standard principal and interest (P&I) loan, each repayment covers both:
- Interest on the outstanding balance, and
- A portion of the principal (reducing the loan balance)
In an interest-only loan, repayments cover only the interest. The loan balance does not reduce during the IO period.
Example — $500,000 loan at 6.5%:
| Loan type | Monthly repayment | Principal repaid | Balance after 5 years |
|---|---|---|---|
| P&I (25-year term) | ~$3,375 | ~$40,000 | ~$460,000 |
| IO (5-year IO period) | ~$2,708 | $0 | $500,000 |
The IO loan has lower monthly repayments during the IO period — but the loan balance is unchanged.
Why Property Investors Use Interest-Only Loans
1. Tax deductibility
Mortgage interest on an investment property is deductible against rental income. Principal repayments are not deductible — they are a return of capital. By using IO, the entire repayment is deductible, maximising the tax benefit.
Under a P&I loan, as the principal reduces over time, the interest component of each repayment also reduces — shrinking the deductible amount year by year.
2. Cash flow management
IO repayments are lower than P&I, leaving more monthly cash flow. For negatively geared investors already topping up a shortfall, lower repayments reduce the out-of-pocket monthly cost.
3. Capital recycling
Some investors use the savings from lower IO repayments to contribute to their owner-occupier mortgage (which is not deductible) — a strategy known as debt recycling. This simultaneously reduces non-deductible debt and maximises deductible investment debt.
When Interest-Only Ends
IO periods are finite. When the IO period expires, the loan reverts to P&I repayments — now calculated over the remaining loan term (original term minus IO period). This creates a repayment step-up — significantly higher monthly payments.
Example — IO period ending:
- Remaining loan: $500,000
- Remaining term: 20 years (was 25 years, 5 years IO)
- New P&I monthly repayment: ~$3,731 (vs $2,708 IO — a $1,023/month increase)
Investors must plan for this transition. Options include:
- Refinancing to a new IO period (subject to lender approval and policy)
- Selling the property before IO ends
- Absorbing the higher P&I repayments from increased rental income or income growth
APRA Restrictions on IO Lending
APRA (Australian Prudential Regulation Authority) has periodically tightened restrictions on interest-only lending. As of 2026:
- IO loans typically require stronger serviceability than P&I loans
- Maximum IO periods are capped (commonly 5 years for investors, extendable on review)
- IO loans for owner-occupiers are less commonly approved
Investor IO lending policy varies by lender — a mortgage broker can identify current IO loan availability.
Interest-Only vs Principal and Interest — Comparison
| Feature | Interest-Only | Principal & Interest |
|---|---|---|
| Monthly repayment | Lower | Higher |
| Loan balance changes | No (during IO period) | Yes — reduces over time |
| Interest deductibility | Full repayment deductible | Only interest portion deductible |
| Build equity faster | No | Yes |
| Cash flow | Better during IO | Lower monthly cash flow |
| Risk | Higher (no equity build-up) | Lower |
Risks of Interest-Only Loans for Investors
- No equity building: During the IO period, no principal is repaid — you rely entirely on capital growth to build equity
- Repayment shock: The transition from IO to P&I increases repayments significantly
- Refinancing risk: If property values fall or lending policy tightens, refinancing at IO period end may not be available
- Interest rate risk: IO rates are typically slightly higher than P&I rates
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Frequently Asked Questions
Is interest-only better for investment properties? IO loans are commonly used by Australian property investors to maximise deductibility and manage cash flow. Whether IO is appropriate depends on your overall financial position, how you plan to manage the loan at IO period end, and your cash flow needs. This is general information — a mortgage broker or financial adviser can assess your specific circumstances.
Can I switch from P&I to IO on my investment loan? Switching from P&I to IO mid-loan is possible but subject to lender approval, current lending policy, and your serviceability at the time. Some lenders allow this easily; others require a full reassessment.
Does interest-only mean I’m paying more total interest? Yes. Because the principal is not reducing during the IO period, total interest paid over the full life of the loan is higher than a P&I loan from the same start date. The trade-off is maximised deductibility and lower repayments during the IO period.
This article provides general financial information only. For advice tailored to your situation, speak with a licensed financial adviser or mortgage broker. You can find a financial adviser through the ASIC financial advisers register or MoneySmart.