P&I vs Interest Only Home Loans: What's the Difference?

When choosing a home loan, one of the most important decisions you'll make is how you structure your repayments. The two core options are Principal and Interest (P&I) and Interest Only (IO). Understanding the difference between principal and interest vs interest only repayments can save you significantly over the life of your loan - or help you manage cash flow during tight periods.

This guide breaks down how each repayment type works, who they suit, and the real cost implications of choosing one over the other. You can also compare current home loan rates to see what lenders are offering right now.

What Is Principal and Interest (P&I)?

Principal and Interest is the standard home loan repayment structure. Each repayment you make is split into two components:

1. Interest - the cost the lender charges you for borrowing the money.
2. Principal - a portion that pays down the actual loan balance.

With every P&I repayment, your outstanding debt decreases. This creates a compounding benefit: as your loan balance shrinks, the interest charged on that balance also reduces, meaning a progressively larger share of each repayment goes towards the principal.

Over a standard 30-year loan term, the majority of your early repayments go towards interest. As the years progress, the split gradually shifts in favour of principal reduction.

Why Choose P&I?

• Pay less total interest - you are constantly reducing the balance that interest is calculated on.
• Build equity - every repayment increases your ownership stake in the property.
• Lower interest rates - lenders typically offer lower rates for P&I loans because they represent lower risk.
• Forced savings - the mandatory principal repayment builds your net worth over time, even if property values remain flat.

For most owner-occupiers, P&I is the default and generally recommended repayment structure.

What Is Interest Only (IO)?

With an Interest Only loan, your repayments cover only the interest charges for a set period - typically 1 to 5 years. During this time, you do not repay any of the loan balance.

Because you are not paying down principal, your monthly repayments are lower than they would be on a P&I loan. However, your loan balance remains completely unchanged throughout the IO period.

To illustrate conceptually: if you were to borrow a given amount and make only interest payments for several years, you would still owe the full original amount at the end of that period. Not a single dollar of debt has been retired.

Why Choose Interest Only?

• Lower initial repayments - useful for short-term cash flow management, such as during parental leave or while renovating a property.
• Potential tax benefits for investors - investors may use IO loans as part of a broader tax strategy to maximise deductible interest expenses. Always consult your accountant for advice specific to your situation.
• Flexibility with offset accounts - some borrowers pair an IO loan with an offset account, keeping repayments low while parking surplus cash to reduce the interest charged.

How Do Repayments Differ Structurally?

The structural difference between P&I and IO is straightforward but has significant long-term consequences.

With P&I, every repayment chips away at the debt. The loan is designed to reach zero at the end of the term. With IO, the debt remains static during the interest-only period - you are essentially renting the money.

This means:

• On a P&I loan, your equity grows with every payment.
• On an IO loan, your equity only grows if the property value increases - you are not contributing to it through repayments.

The current best variable home loan rate is 5.43% p.a. - but keep in mind that IO loans generally attract a higher rate than the equivalent P&I product from the same lender.

The Total Cost Difference Over the Life of the Loan

It is a mathematical certainty that an Interest Only loan costs more over the full life of the loan compared to an equivalent P&I loan, assuming minimum repayments on both. There are two compounding reasons:

1. Interest on a higher balance for longer - since the principal does not decrease during the IO period, you are charged interest on the full loan amount for those years.
2. Higher interest rates - lenders generally charge a rate premium for IO loans to compensate for the additional risk.

The total difference in interest paid can be substantial. While the exact figures depend on your loan amount, rate, and IO period length, the structural reality is that deferring principal repayment always increases total borrowing costs.

Key takeaway: IO repayments are cheaper month-to-month in the short term, but significantly more expensive over the full loan life.

Who Typically Uses Interest Only Loans?

Interest Only loans are a specialised product. They are most commonly used by:

Property Investors

Investors often prefer IO loans as part of a tax minimisation strategy. In Australia, interest on an investment loan is generally tax-deductible. By keeping the loan balance high (and interest payments maximised), investors can increase their deductions. Surplus cash flow may then be directed towards paying down non-deductible debt, such as an owner-occupier home loan.

This is a general overview of a common strategy and does not constitute tax advice. Always consult a qualified tax professional before making financial decisions based on tax considerations.

For more on investment lending strategies, see our guide to investment property loans.

Renovators and Short-Term Holders

If you buy a property to renovate and sell within a short timeframe, IO can keep your holding costs low during the project. Since the intention is to repay the loan in full upon sale, minimising monthly outgoings during the holding period may be a priority.

Borrowers with Temporary Cash Flow Constraints

Some owner-occupiers use IO for a short period to navigate a temporary reduction in income - for example, during parental leave or a career transition. However, this is less common now due to stricter lending assessments.

The "Interest Only Cliff" - What Happens When the IO Period Ends

One of the most significant risks with IO loans is the repayment shock that occurs when the interest-only period expires.

When the IO term ends, the loan automatically reverts to Principal and Interest repayments. However, you now have a shorter remaining term to pay off the same original balance.

Conceptual example:

• Total loan term: 30 years
• IO period: 5 years
• Remaining P&I term: 25 years

Instead of spreading principal repayments over 30 years, you must now repay the full balance in just 25 years. This compression means your repayments can jump significantly - not just because you are now paying principal, but because you are paying it back over a shorter period.

Borrowers who do not plan for this transition can find themselves under serious financial stress. It is essential to understand your post-IO repayment obligations before committing to an IO loan, as noted by Moneysmart's home loan guidance.

APRA Restrictions on Interest Only Lending

The Australian Prudential Regulation Authority (APRA) has historically intervened to tighten lending standards around Interest Only loans, particularly during periods of rapid credit growth.

As a result of these regulatory expectations, lenders now typically:

• Charge higher interest rates for IO loans compared to P&I.
• Require borrowers to demonstrate they can service the loan at P&I repayments after the IO period ends.
• Apply stricter loan-to-value ratio (LVR) requirements for IO applicants.
• Limit IO periods, often to a maximum of 5 years.

These measures are designed to reduce systemic risk and ensure borrowers are not overextending themselves. For more detail, refer to APRA's guidance on residential mortgage lending standards.

Pros and Cons at a Glance

How to Decide Which Repayment Type Suits You

The right choice depends on your financial goals, property strategy, and risk tolerance.

P&I is generally the better choice if you:

• Want to pay off your home loan and become debt-free sooner.
• Want access to the lowest available interest rates.
• Are buying a home to live in (owner-occupier).
• Want to build equity steadily with every repayment.

IO may be worth considering if you:

• Are an investor with a tax strategy that benefits from higher deductible interest (consult your accountant).
• Need to minimise cash outflows for a defined, short-term period.
• Have a disciplined plan to direct saved cash flow towards paying down other, non-deductible debt.
• Understand and have planned for the repayment increase when the IO period ends.

Whichever option you are leaning towards, compare home loan rates across 2360 products to ensure you are getting a competitive deal.