ON THE BLOG

Interest-Only vs Principal-and-Interest Home Loans: Which Is Right for You?

When structuring a home loan — especially for an investment property — the choice between interest-only (IO) and principal-and-interest (P&I) repayments can have a significant impact on your cashflow, your tax position, and the total cost of your loan over time.

The decision is not simply about which repayment is lower. It involves your investment strategy, income tax situation, equity-building goals, and what happens when an IO period expires.

How Interest-Only Loans Work

With an IO loan, you pay only the interest component for a set period — typically five years for investment properties. During this time, your loan balance does not decrease. You are not building equity through repayments — only through any capital growth in the property.

For investors, the appeal is clear: lower monthly repayments mean better cashflow during the IO period, and because the entire repayment is interest, the entire repayment is tax-deductible. This is particularly relevant for negatively geared investors. See our negative gearing guide to understand how this interacts with your tax position.

How Principal-and-Interest Loans Work

With a P&I loan, each repayment covers both the interest accrued and a portion of the principal. Over time, your loan balance decreases, your equity increases, and the interest component of each repayment falls. P&I loans typically attract a lower interest rate than IO loans — in 2026, the rate difference is commonly 0.3% to 0.6% per annum depending on the lender.

IO vs P&I on a $500,000 Investment Loan: Worked Example

Comparing the total cost of a $500,000 investment loan over 30 years under IO versus P&I repayments:

Assumptions: $500,000 loan, 30-year term. P&I rate: 6.10% p.a. IO rate: 6.50% p.a. (0.40% premium). IO period: 5 years, then reverts to P&I for the remaining 25 years.

	P&I from day one	IO 5 years then P&I
Monthly repayment years 1–5	~$3,037	~$2,708 (IO at 6.50%)
Monthly cashflow saving during IO	—	~$329/month
Loan balance after 5 years	~$461,000	$500,000 (no reduction)
Repayments years 6–30 (P&I revert)	~$2,900	~$3,375 (higher balance)
Total interest over 30 years	~$593,000	~$698,000
Total cost difference	—	~$105,000 more

The IO option saves approximately $329 per month ($19,740 over 5 years) in repayments. The trade-off is roughly $105,000 in additional total interest over the life of the loan. For a deeper look at how loan structure affects investment returns, see our investment property loan options page.

IO Period Limits: What You Need to Know

APRA regulates IO period length:

Owner-occupier loans: Maximum 5 years IO over the life of the loan
Investment loans: Maximum 10 years IO over the life of the loan, subject to at least 5 years remaining on the contracted term

When the IO period ends, repayments automatically switch to P&I, calculated on the remaining balance over the remaining term. Because no principal was repaid during the IO period, the P&I repayments after the switch are higher than they would have been with P&I from day one.

When IO Makes Strategic Sense

Investors Prioritising Tax Efficiency

For a negatively geared investor, every dollar of interest paid is a dollar of tax deduction. IO maximises deductible interest in the short term and preserves capital that can be deployed into an offset account on an owner-occupied property — generating a tax-free return equivalent to the interest rate. This strategy is widely used in Australian property investment. Visit our property investment hub for the full strategic picture.

Short-Term Hold or Construction Period

If you plan to sell within the IO period, or the property is under renovation, IO reduces cashflow pressure during a period when rental income may be limited or absent.

When P&I Is the Better Choice

Owner-Occupiers Building Equity

For your principal place of residence, home loan interest is not tax-deductible — so the case for IO is weak. P&I builds equity faster, reduces the loan balance, and lowers total interest paid. It also puts you in a stronger refinancing position over time. See the home loans page to compare P&I products currently available.

Long-Term Buy-and-Hold Investors

If you intend to hold the property for 20–30 years, the $105,000 additional total interest in the example above is a real long-term cost. Investors with strong cashflow who don’t need to preserve every dollar each month are often better served by P&I from the outset.

When Your IO Period Is About to Expire

If your IO period is ending in the next 6–12 months, you face a repayment increase as the loan switches to P&I. This is one of the most common triggers for refinancing reviews. If your current lender’s revert rate is uncompetitive, switching to a new P&I loan at a better rate may save thousands. See our refinancing guide for how to assess your options.

FAQ

Can I switch from IO to P&I before the IO period ends?

Yes. Most lenders allow you to switch at any time without penalty. As the rate differential between IO and P&I narrows, it often makes financial sense to switch early. Your broker can model whether switching would benefit your current position.

Does choosing IO affect my borrowing capacity?

Yes, significantly. Lenders assess serviceability based on P&I repayments regardless of whether you select IO. Some lenders also apply a higher interest rate for IO loans in their serviceability assessment, further reducing assessed borrowing capacity. This is worth modelling before you choose an IO structure.

What happens if I can’t afford repayments when my IO period expires?

This is IO expiry risk. The P&I repayments after IO expires are higher than equivalent P&I repayments from day one, because the loan balance hasn’t reduced. If your financial position hasn’t improved — or rates have risen — the jump can be significant. Review your loan before expiry, not after the first elevated repayment arrives.

Is IO suitable for owner-occupiers?

It’s available — with a maximum 5-year IO period — but rarely optimal. Owner-occupier home loan interest is not tax-deductible, and IO simply delays equity-building while increasing total interest paid. Most owner-occupiers are better served by P&I from the outset.

Not Sure Which Structure Is Right for You?

The right loan structure depends on your goals, tax position and cashflow. Lagos Financial works with investors and owner-occupiers across Australia to structure loans that support both short-term cashflow and long-term wealth building. Book a complimentary assessment and let’s run the numbers for your situation.

Explore our full guide on interest-only home loan options.