Everything You Need to Know About Investment Loan Optimisation

What Investment Loan Optimisation Actually Means

Investment loan optimisation means structuring your borrowing to match your cash flow, tax position and long-term property goals rather than accepting a standard loan product. This involves choosing the right repayment type, splitting your loan strategically, and ensuring your loan features support portfolio growth without locking you into unnecessary costs.

Many investors in Carnegie refinance within two years because their initial loan no longer suits their circumstances. They might have chosen interest-only to maximise cash flow but failed to consider how long that period would last, or locked in a fixed rate without keeping a portion variable for extra repayments. The loan that works at purchase rarely works five years later without adjustment.

Consider an investor who bought a two-bedroom unit near Koornang Road. They took a standard principal and interest loan at 80 per cent LVR with a basic variable rate. Eighteen months later, they wanted to buy a second property but discovered they had minimal equity growth and their borrowing capacity was reduced by the principal repayments. Refinancing to interest-only and negotiating a lower rate freed up $620 per month in cash flow and increased their serviceability enough to access a second deposit through equity release.

Interest-Only vs Principal and Interest for Investors

Interest-only repayments reduce your monthly outgoings and preserve cash flow, which improves your ability to service additional loans. Principal and interest repayments build equity faster and reduce your overall loan balance, which lowers risk and can improve future refinancing outcomes.

The decision depends on whether you're prioritising cash flow for portfolio growth or equity reduction for long-term security. In our experience, investors planning to acquire multiple properties within five years benefit from interest-only during the accumulation phase, while those holding a single investment long-term often switch to principal and interest once their income increases or their owner-occupied debt is cleared.

Interest-only periods are typically available for one to five years on investment loans, after which the loan reverts to principal and interest unless you request an extension. Extensions are subject to lender criteria and may not be approved if your circumstances have changed. If you're relying on interest-only to make the investment viable, build a buffer for the reversion or plan to refinance before the period ends.

How Fixed and Variable Rate Splits Support Flexibility

Splitting your investment loan between fixed and variable portions lets you lock in certainty on part of your debt while retaining flexibility on the rest. The variable portion allows extra repayments without penalty, offset account access in some cases, and rate discounts that may not be available on fixed products.

A common split is 50-50 or 60-40 in favour of variable, depending on your risk tolerance and whether you expect to make lump sum repayments. Investors with irregular income, such as commission or bonuses, often keep a larger variable portion so they can park surplus funds in an offset account linked to that split. Those with steady salary income and a preference for certainty may fix a larger portion, particularly if they're not planning to make extra repayments.

Be aware that fixed rate loans often carry break costs if you repay early, refinance or sell the property before the fixed term ends. These costs can be significant if interest rates have fallen since you fixed. For this reason, fixing 100 per cent of an investment loan is rarely optimal unless you're certain you won't need to access equity or sell within the fixed period.

Structuring Loans to Preserve Deductibility

Interest on borrowings is only deductible if the funds are used to produce assessable income. If you draw down on your investment loan for private purposes, such as renovating your own home or buying a car, that portion of the interest becomes non-deductible.

This becomes particularly relevant when accessing equity. If you refinance your investment property to release equity, the interest on that additional borrowing is only deductible if the funds are used for income-producing purposes, such as a deposit on another investment property. Using the same funds for a holiday or private expense means the interest on that portion is not claimable.

The safest approach is to keep investment and private borrowings in separate loan accounts. Many lenders allow you to split a single security into multiple loan accounts, each with its own purpose and interest calculation. This separation makes record-keeping straightforward and ensures your deductions are defensible if reviewed.

Rate Discounts and How to Access Them

Most lenders publish a standard variable rate but offer discounts based on loan size, LVR and relationship value. A discount of 0.70 to 1.00 percentage points below the standard rate is common for investment loans at 80 per cent LVR or below, though this varies between lenders and changes frequently.

Discounts are not automatic. They're negotiated at application and review, and often depend on whether you're bringing multiple products to the lender, such as packaging your owner-occupied loan and investment loan together. Investors who accept the first rate offered often pay more than those who compare across lenders or work with a broker to access portfolio pricing.

Rate discounts can erode over time. Lenders typically reserve their most competitive pricing for new customers, so a loan that was discounted at settlement may no longer be competitive two years later. An investment loan refinance review every 18 to 24 months ensures you're not overpaying as market pricing shifts.

Loan Features That Support Portfolio Growth

The features that matter for investors differ from those that matter for owner-occupiers. Offset accounts, redraw facilities and the ability to capitalise Lenders Mortgage Insurance all influence cash flow and serviceability.

Offset accounts linked to variable investment loans reduce the interest charged without reducing the loan balance. This preserves your deductible debt while lowering your actual interest cost. Redraw facilities allow you to access extra repayments you've made, though some lenders restrict redraw on investment loans or charge fees for access.

Capitalising LMI means adding the premium to your loan amount rather than paying it upfront. This preserves your cash for other purposes, such as holding costs or a deposit on the next property. The trade-off is that you'll pay interest on the LMI amount over the life of the loan, and your LVR will be slightly higher at settlement.

If you're planning to build a portfolio, ensure your loan allows you to use the property as security for future borrowing without requiring a full refinance. Some lenders restrict further advances or require you to reapply at current serviceability standards, which can block access to your own equity if lending conditions have tightened.

What Changes from 1 July 2027

The Treasury Laws Amendment (Tax Reform No. 1) Act 2026 introduces quarantining of rental losses for residential properties acquired on or after 7:30pm AEST on 12 May 2026, effective from 1 July 2027. Losses from these properties can only be offset against other residential rental income or carried forward, not against salary or wages.

Properties held before that date, including those under contract at the time, are grandfathered and may continue to be negatively geared under existing rules. Eligible new builds, defined as dwellings constructed on previously vacant land or where the number of dwellings increases, remain fully negatively gearable even if purchased after the cut-off.

This changes the cash flow equation for many investors. If you're buying an established property in Carnegie now, rental losses from 1 July 2027 onward won't reduce your tax on employment income. That means you'll need stronger rental yield or larger cash reserves to sustain the holding costs. Investors targeting portfolio growth may shift focus to new builds or reassess their acquisition timeline to bring forward purchases while grandfathering still applies.

The CGT discount is also being replaced with cost base indexation and a minimum 30 per cent tax rate on real gains for assets acquired after the same date, though gains accrued before 1 July 2027 continue under current rules. Eligible new builds retain an election between the 50 per cent discount and indexation.

Investors routinely underestimate how much serviceability matters when scaling a portfolio. Your borrowing capacity is calculated on principal and interest repayments at the loan rate plus a 3 percentage point buffer, regardless of whether you're actually paying interest-only. Choosing interest-only doesn't increase your serviceability in the lender's eyes, but it does improve your actual cash flow, which gives you breathing room to save the next deposit or manage vacancies.

Carnegie's vacancy rate has historically been low due to its proximity to Monash University, Caulfield Hospital and the Glen Eira employment precinct, but a vacancy still means covering the full loan repayment from your own income. Structuring your loan with an offset or redraw lets you build a buffer during tenanted periods that you can draw on if the property sits empty between leases.

The calculation also includes body corporate fees for units, which are common in Carnegie's medium-density precincts around the train station. A $1,500 per quarter body corporate fee reduces your serviceability by roughly $35,000 in borrowing capacity under current settings. If you're comparing a unit with high fees against a standalone townhouse, factor that difference into your purchase price limit, not just the strata costs themselves.

When to Refinance Your Investment Loan

Refinancing makes sense when your rate is no longer competitive, your loan features don't support your current strategy, or you need to access equity for the next purchase. It doesn't make sense if the cost of exit fees, application fees and valuation charges exceeds the benefit over the period you plan to hold the new loan.

A difference of 0.50 percentage points on a $600,000 loan saves roughly $3,000 per year in interest. If refinancing costs $2,500 in total fees, you'll break even in ten months. If your circumstances have changed and you're likely to sell or refinance again within 12 months, the benefit is marginal.

Timing matters. Refinancing before you apply for additional finance ensures your existing investment loan is optimised for serviceability and won't limit your next purchase. Refinancing after you've secured the next property can be harder because your debt levels have increased and lenders apply current serviceability buffers to the new total.

If your fixed rate is due to expire, review your options at least 90 days before the end of the fixed term. Lenders often send renewal notices 30 days out, but by that stage your choices are limited to what your current lender offers. Comparing across lenders earlier gives you time to apply, value the property and settle the refinance without reverting to a higher variable rate in the interim.

Setting up your investment loan correctly from the start saves time and money later. Work with someone who understands how loan structure affects both your immediate cash flow and your ability to grow the portfolio over time. If you're buying in Carnegie or holding property elsewhere and want to make sure your borrowing is aligned with your investment strategy, call one of our team or book an appointment at a time that works for you.

Important: This does not constitute tax advice and it is recommended to seek advice from your Accountant or Financial Planner for your individual circumstances.