Interest-only loans on investment properties were extremely popular before tighter lending rules came into force. They still have their place — but the logic for using them is more nuanced than most investors realise.
1–5 yrs
Typical IO period
+0.2%
Rate premium vs P&I
Lower
Monthly repayments
Tax
Maximises deductions
How Interest-Only Investment Loans Work
On an interest-only (IO) investment loan, you only pay the interest portion of the loan each month — you do not pay down the principal. The loan balance stays the same for the interest-only period (typically 1–5 years).
After the interest-only period expires, the loan automatically converts to principal and interest (P&I) — and repayments increase significantly because you now have to repay the full principal over the remaining loan term.
Numerical comparison — $650,000 loan at 7.0%
| Loan Type | Monthly Repayment | Monthly Saving vs P&I |
|---|---|---|
| Interest-Only (IO) | $3,792 | +$821 |
| Principal & Interest (P&I) — 30yr | $4,325 | — |
| P&I — 25yr | $4,613 | — |
IO rate typically +0.2–0.4% vs P&I. Monthly saving is real — but the total interest over the life of the loan is higher with IO.
Why Investors Use Interest-Only Loans
There are two main reasons investors choose IO:
1. Cash Flow Management
For a negatively geared property, the lower IO repayment reduces the monthly out-of-pocket cost. The $821/month saving in the example above is $9,852 per year — meaningful cash flow that can be redirected to the owner-occupied mortgage (which is not tax-deductible) or toward another investment deposit.
2. Tax Strategy (Debt Recycling / Portfolio Structure)
Interest payments on investment loans are fully tax-deductible. Principal repayments are not. By keeping investment loan balances high (IO — not paying down principal), the deductible interest remains maximised.
At the same time, a financially sophisticated investor makes extra repayments into their owner-occupied home loan (which is not deductible) — reducing non-deductible debt while keeping deductible investment debt high. This is called "debt recycling" or "debt optimisation" and can substantially improve overall after-tax returns.
Important: Get tax advice specific to your situation
The tax implications of IO vs P&I are real and can be significant. Always speak with a qualified accountant before choosing your loan structure for tax reasons. The analysis differs based on your personal income, other investments, ownership structure, and plans.
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The Risks of Interest-Only Investment Loans
- No equity built during IO period: If property values fall during the IO period, you may have negative equity (owe more than the property is worth)
- Payment shock at IO expiry: When the IO period ends and the loan converts to P&I, repayments increase significantly — sometimes by $500–$1,000+/month. Investors who don't plan for this are caught out.
- Higher total interest cost: Paying no principal for 5 years means paying interest on the full balance for 5 years longer. Total interest over the life of the loan is higher with IO than P&I.
- Refinancing risk: If you need to refinance at IO expiry and your situation has changed (income, credit, property value), you may be forced onto P&I at a less favourable rate.
- Tighter approval criteria: Since APRA's 2017 intervention, IO investment loans are more closely scrutinised. Lenders assess your ability to service at the P&I rate, not just the IO rate.
Lender Assessment: What's Changed Since 2017
Before 2017, IO investment loans were easy to obtain with minimal scrutiny. APRA (the banking regulator) imposed restrictions that changed this:
- Lenders must assess your ability to repay at the P&I rate (not just the IO rate) even during the IO period
- IO loans on investment properties are subject to an additional serviceability "buffer" at most lenders
- Maximum IO periods are typically capped at 5 years (some lenders allow 10, but rare)
- Total IO exposure across the banking system is regulated — some lenders hit caps and temporarily withdrew IO products
When Interest-Only Makes Sense in 2026
- You're negatively geared and the IO saving is being directed to your owner-occupied loan or next investment deposit
- You're on a high marginal tax rate and maximising deductible debt is part of a deliberate tax strategy (confirmed with an accountant)
- The IO period aligns with a planned sale or refinance timeline (e.g., you plan to sell or refinance in 3 years)
- Cash flow is genuinely tight and the lower repayment is needed to maintain serviceability
When P&I Is Better for Investment Property
- You're positively geared and don't need the cash flow benefit of IO
- You're on a lower tax rate and the deduction benefit is modest
- You want to build equity faster to access for the next purchase
- You're approaching retirement and want to reduce debt
- You're at risk of payment shock — better to manage repayments progressively than face a cliff
At Mortgagefy, we compare both IO and P&I options across 30+ lenders for investment loans and help you model the real after-tax cash flow for each. We work with property investors across Western and Southwest Sydney — Liverpool, Parramatta, Campbelltown, and the broader region. Free consultation — call 0432 634 648.
See also: Negative Gearing Explained | Investment Property Loans | How to Use Equity to Buy an Investment Property.
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