Interest-only vs principal and interest home loans explained. Compare costs, repayments, pros and cons. Find which loan structure suits you. Brokio, Melbourne.
When you take out a home loan, you'll choose between two repayment structures: interest-only (IO) or principal and interest (P&I). The difference isn't just about what you pay each month — it fundamentally changes how your loan behaves over time.
With a P&I loan, every repayment covers two things:
In the early years, most of your repayment goes toward interest. Over time, as the balance shrinks, more goes toward principal. This is called amortisation — and it's how most Australian home loans work.
On a $600,000 loan at 6.10% over 30 years, your monthly P&I repayment would be approximately $3,640. By the end of the 30 years, the loan is fully repaid.
With an interest-only loan, you only pay the interest charged on the loan — none of your payment reduces the principal balance. The amount you owe stays the same throughout the IO period.
IO periods in Australia typically last 1 to 5 years (up to 10 years for investment loans with some lenders). After the IO period ends, the loan automatically converts to P&I — and your repayments jump significantly because you now have to repay the full principal in a shorter remaining term.
On the same $600,000 loan at 6.10%, your monthly IO repayment would be approximately $3,050 — about $590 less per month than P&I.
Interest-only loans typically carry a higher interest rate than equivalent P&I loans. As of early 2026, the premium is roughly 0.50–0.90% p.a. depending on the lender and whether the property is owner-occupied or an investment. This rate gap exists because IO loans are considered higher risk by lenders — you're not reducing the debt, and APRA (Australia's banking regulator) has historically scrutinised IO lending more closely.
| Feature | Principal & Interest | Interest-Only |
|---|---|---|
| Monthly repayments | Higher initially | Lower during IO period |
| Loan balance | Decreases over time | Stays the same during IO period |
| Total interest paid | Less over loan life | More over loan life |
| Interest rate | Lower (standard rate) | Higher (IO premium ~0.50–0.90%) |
| Equity building | Yes — from day one | No — relies on property growth |
| Best for | Owner-occupiers, long-term wealth | Investors, short-term cash flow |
The monthly savings from interest-only repayments can look attractive — but the long-term cost tells a very different story. Let's run the numbers on a realistic scenario.
| Factor | P&I (30 Years) | IO 5 Years → P&I 25 Years |
|---|---|---|
| Interest rate | 6.10% p.a. | 6.70% (IO) → 6.10% (P&I) |
| Monthly repayment (Years 1–5) | $3,640 | $3,350 |
| Monthly repayment (Years 6–30) | $3,640 | $3,920 |
| Total interest paid | $710,400 | $877,600 |
| Total cost of loan | $1,310,400 | $1,477,600 |
| Extra cost of IO structure | — | $167,200 more |
That five-year IO period saves you about $290/month in the short term — but costs you an extra $167,200 over the life of the loan. And your repayments increase after the IO period because you still owe the full $600,000 but now have only 25 years to repay it.
Three factors compound the cost of IO loans:
The $17,400 saved during the 5-year IO period (approximately $290 × 60 months) is dwarfed by the $167,200 extra you pay over the remaining 25 years. Unless you invested those monthly savings at a return significantly exceeding your loan rate — and actually did so consistently — the maths doesn't work for most owner-occupiers.
This is why Brokio always recommends P&I for owner-occupiers unless there's a specific strategic reason for IO (which we'll cover in the next sections).
Despite the higher long-term cost, interest-only loans are a legitimate strategy for certain borrowers. Here's when IO can make financial sense.
IO loans are most commonly used by property investors, and for good reason:
Example: Sarah has a $500,000 home loan (non-deductible) and a $400,000 investment loan (deductible). By putting the investment loan on IO and directing the monthly savings toward her home loan, she pays off her non-deductible debt faster while maintaining the tax-efficient investment structure.
If you're buying a new home before selling your current one, IO on one or both loans can keep repayments manageable during the overlap period. This is a temporary strategy — typically 6 to 12 months — and makes sense when you have a clear exit plan (i.e., the sale of your existing property).
In limited cases, IO can help borrowers who are genuinely expecting a substantial income increase within the next 1–2 years — for example, a medical specialist completing their final year of training before entering full practice. But be honest with yourself: "I might get a pay rise" isn't the same as "I'm completing specialist training with a guaranteed salary jump."
If you're purchasing a property to renovate and sell (or substantially improve before refinancing), IO during the renovation period keeps costs low while you add value. The loan should convert to P&I or be refinanced once the project is complete.
Even for investors, IO isn't always the best choice. With APRA's February 2026 debt-to-income (DTI) caps limiting high-DTI lending to 20% of new mortgages, having a large IO balance can make it harder to borrow for your next property. Lenders assess IO loans at the higher P&I repayment for serviceability — so the cash flow benefit doesn't help your borrowing power as much as you might think.
For most Australian borrowers — and especially most owner-occupiers — P&I is the right choice. Here's why.
If you're living in the property, there is no tax deduction on your mortgage interest. Every dollar of interest is a pure cost. P&I repayments actively reduce that cost over time by shrinking the balance you're charged interest on. Going IO as an owner-occupier means you're paying more interest on a balance that never decreases — and you're not getting any tax benefit for doing so.
It's tempting for first home buyers to choose IO to keep initial repayments low. But this is one of the riskiest uses of IO. You're already at maximum stretch, you haven't built any equity buffer, and you're banking on property growth to build your wealth instead of actual principal repayment. If the market dips or stays flat during your IO period, you could end up owing more than the property is worth (negative equity) with even higher repayments looming.
At Brokio, we rarely recommend IO for first home buyers. If the only way to afford the repayments is to go IO, you may be borrowing too much.
P&I is a forced savings mechanism. Every month, a portion of your repayment builds equity in your home — equity you can later use for renovations, investment, or simply as financial security. After 10 years of P&I repayments on a $600,000 loan at 6.10%, you'll have paid down approximately $120,000 in principal. With an IO loan, your balance after 10 years? Still $600,000 (assuming you extended or refinanced the IO period).
P&I loans consistently attract lower interest rates than IO equivalents. As of early 2026:
That 0.50% gap might seem small, but on a $600,000 loan it's $3,000 per year in extra interest — just for the privilege of not reducing your balance.
The only way IO makes financial sense is if the monthly savings are deployed strategically — paying down non-deductible debt, invested in assets earning above your loan rate, or used for a specific short-term purpose. If the savings would just disappear into general spending (which research shows happens in most cases), you're worse off. P&I imposes the discipline automatically.
The biggest risk with IO loans isn't the monthly savings — it's what happens when the IO period expires. This is known as the "interest-only cliff", and it catches borrowers off guard every year.
When your IO period ends, the loan automatically converts to P&I. But you now have fewer years to repay the full principal. Here's what that looks like:
For a borrower who chose IO because P&I was already at the edge of their budget, this jump can be devastating. And it gets worse with longer IO periods — a 10-year IO period on an investment loan means you have only 20 years to repay the full principal, pushing monthly repayments even higher.
When the IO cliff hits and borrowers can't manage the higher P&I repayments, they typically have three options — none of them ideal:
Australia's banking regulator APRA has been actively tightening lending standards. Since February 2026, the new debt-to-income (DTI) caps limit banks to issuing no more than 20% of new mortgage lending with a DTI ratio of 6 or above. This makes it harder for IO borrowers to refinance into a new IO period — particularly investors with multiple properties who already have high DTI ratios.
In practice, this means the "just refinance when the IO period ends" strategy is no longer as reliable as it once was. You need to plan for the P&I conversion from day one.
If you do choose IO, the smart approach is to:
Choosing between IO and P&I isn't a one-size-fits-all decision — and it's not one you should make based on a blog post alone. The right structure depends on your complete financial picture.
When clients ask us about IO vs P&I, we look at:
For the majority of our clients — particularly owner-occupiers and first home buyers — we recommend P&I. The lower interest rate, forced equity building, and predictable repayments make it the safer and cheaper option over the life of the loan.
For property investors with a clear tax strategy and the discipline to deploy IO savings productively, IO can be the right choice — but only with a solid exit plan for when the IO period ends.
One thing many borrowers don't realise: you can often switch between IO and P&I during the loan's life without refinancing entirely. Some lenders allow you to convert from P&I to IO (with credit approval) or from IO to P&I at any time. The fees and conditions vary by lender — this is where having a broker who knows the fine print saves you time and money.
For investors, we sometimes recommend a split loan: part IO, part P&I. This balances cash flow benefits with some principal reduction. For example, a $500,000 investment loan might be split into $300,000 IO (maximising tax-deductible interest) and $200,000 P&I (building some equity as a buffer). The right split depends on your overall portfolio and tax position.
Not sure which structure is right for you? Book a free consultation with Brokio. We'll model both scenarios with your actual numbers — income, expenses, tax position, and goals — and show you exactly what each option costs over 5, 10, and 30 years. No jargon, no pressure, just clear numbers.
Visit us at 601/87 Overton Road, Williams Landing VIC 3027, or call for a phone consultation. We help borrowers across Williams Landing, Point Cook, Tarneit, Truganina, Werribee, and all of Melbourne's western suburbs make smarter loan decisions.
Ready to explore tailored loan options? Contact Brokio today and let us guide you through your mortgage, car loan, personal loan, or investment property loan journey with confidence.
