Simple hacks to lock in fixed rates on investment loans

A fixed rate investment loan gives you certainty over your borrowing costs for a set period, usually between one and five years.

That certainty carries a different weight now that negative gearing rules change from 1 July 2027. If you acquire an established residential property on or after 7:30pm AEST on 12 May 2026, rental losses will be quarantined and cannot be offset against your judicial salary. Only rental income from other properties or future capital gains on residential property can absorb those losses. For properties acquired before that date and time, existing negative gearing rules continue to apply. The shift means your capacity to service an investment loan depends more heavily on rental income and less on tax offsets from other income.

Fixed Rate Investment Loan Features That Matter

Fixed rate investment loans lock your interest rate for a term you select at the time of settlement. Most lenders offer one, two, three, four and five-year terms. During that period, your principal and interest repayments remain constant regardless of Reserve Bank cash rate movements. Interest-only repayments, where permitted, are also fixed for the term.

The trade-off is reduced flexibility. Most fixed rate products limit additional repayments to between $10,000 and $30,000 per year without triggering break costs. If you sell the property, refinance to another lender, or switch to a variable rate before the fixed term ends, the lender will calculate break costs based on the difference between your contracted rate and the wholesale rate the lender can now achieve for the remaining term. Those costs can run to tens of thousands of dollars if rates have fallen significantly since you fixed.

Some lenders offer partial offset accounts on fixed rate investment loans, though the offset percentage is usually capped at 40 per cent to 60 per cent of the loan balance. Others do not permit offset accounts at all on fixed rate products. If you carry surplus cash for vacancy buffers or upcoming settlement costs on another property, the inability to fully offset that balance against your investment loan interest can reduce after-tax returns.

When Rate Certainty Outweighs Flexibility

You value certainty over flexibility when your serviceability sits close to a lender's maximum debt-to-income ratio or when rental income covers a high proportion of the loan repayment. Under APRA's prudential settings effective from 1 February 2026, lenders may allocate no more than 20 per cent of new investor loans to borrowers with a debt-to-income ratio of six times or greater. If your total debt sits near that threshold, fixing part or all of your investment loan prevents a rate rise from pushing you into a position where refinancing becomes difficult or additional borrowing is declined.

Consider an investor who acquired an established apartment in May 2026 before the negative gearing cut-off. Rental income is $42,000 per year and the loan is $620,000. At a variable rate, a 100 basis point rise over two years increases annual repayments by around $6,200 on a principal and interest loan. If the investor cannot offset that increase against other income due to marginal tax bracket changes or a shift to part-time sitting arrangements, the property may move from neutral cash flow to a material cash drain. Fixing the rate for three years at the time of purchase would have locked in known repayments and avoided that risk during the period before the investor builds additional equity or reduces other debts.

How Fixed Rates Apply to New Build Investment Properties

Eligible new build residential dwellings acquired on or after 7:30pm AEST on 12 May 2026 retain access to traditional negative gearing. A new build is defined as a dwelling constructed on previously vacant land or a development that increases the total number of dwellings on a site. A knock-down rebuild that does not increase dwelling numbers does not qualify. If a new build is occupied for more than 12 months before you acquire it, the property loses its new build status for negative gearing purposes.

If you are financing a new build, fixing your rate during construction or at practical completion can lock in serviceability while you still have the ability to offset rental losses against your salary. Once the transition period ends on 30 June 2027, any new build property you acquire will allow ongoing negative gearing, but established properties will not. The ability to deduct interest in full against all income makes cash flow more predictable and reduces the risk that a rate rise forces a sale before you have held the property long enough to crystallise a meaningful capital gain.

New builds also qualify for an election at the time of sale: you can choose between the 50 per cent capital gains tax discount or cost base indexation with a 30 per cent minimum tax rate on real gains. The election allows you to model the sale before settling on a disposal strategy, but fixing your borrowing costs during the hold period remains a separate decision tied to your income stability and risk tolerance.

Split Rate Structures on Investment Loans

A split rate loan divides your total borrowing between a fixed portion and a variable portion. The fixed portion provides repayment certainty, while the variable portion preserves offset capability and penalty-free additional repayments. Common splits are 50/50, 60/40 or 70/30 fixed to variable, though you can nominate any proportion that suits your cash flow and risk profile.

If you hold multiple investment properties, you might fix the loan on a property with lower rental yield or higher vacancy risk and leave the loan on a high-yield property with stable tenancy on a variable rate with full offset. That structure stabilises your highest-risk repayment while keeping flexibility on the property that generates surplus cash. It also allows you to make lump sum repayments from bonuses or distributions without incurring break costs, provided those payments are directed to the variable portion.

Some lenders permit multiple fixed rate tranches with different end dates, so you can stagger your exposure to rate resets. If you fix $300,000 for two years and another $300,000 for four years, only half your loan faces refinancing risk at the two-year mark. That approach smooths your interest rate risk over time and avoids a single large exposure to whatever the market rate happens to be on one specific date.

Refinancing Fixed Rate Investment Loans

Refinancing a fixed rate investment loan before the term expires triggers break costs unless the lender waives them as part of a retention offer. Break costs are calculated using the lender's wholesale funding cost for the remaining term. If you fixed at 5.8 per cent for five years and wholesale rates have since fallen to 4.6 per cent, the lender will charge you the present value of the difference for the remaining period. On a $500,000 loan with three years remaining, that difference can exceed $15,000.

If you are considering investment loan refinancing, run the numbers at least six months before your fixed term ends. Some lenders offer rate-lock facilities that let you secure a new fixed or variable rate up to 90 days before your current term expires, which prevents you from being forced onto a higher revert rate while you complete the refinance process. If your fixed term is ending and you want to remain with the same lender, ask whether a formal refinance is required or whether the lender will simply allow you to select a new fixed or variable rate at expiry without a new application.

For properties acquired after the negative gearing cut-off, the lack of tax relief on rental losses makes refinancing to access equity release more complex. If you have built $150,000 in equity and want to use it as a deposit on another investment property, pulling that equity out increases your loan balance and your repayments on the original property. Those higher repayments cannot be fully offset against your salary if the property was acquired after 7:30pm AEST on 12 May 2026, so you need enough rental income across your portfolio to service both loans without relying on tax deductions from other income.

Calculating Investment Loan Repayments on Fixed Rates

Lenders calculate your serviceability using the actual fixed rate plus a three percentage point buffer, as required under APS 220. If you are applying for a fixed rate of 5.5 per cent, the lender will assess whether you can service the loan at 8.5 per cent. That buffer applies to both principal and interest loans and interest-only loans. Rental income is shaded by a vacancy factor, typically 20 per cent to 25 per cent, meaning the lender will only count 75 per cent to 80 per cent of the gross rent when calculating your borrowing capacity.

If you are purchasing an investment property under the new negative gearing rules, the lender will also consider whether your salary alone can service the shortfall, since rental losses cannot be offset. That assessment depends on your total debt-to-income ratio and whether you fall within the 20 per cent allocation that lenders can make to borrowers at or above six times income.

Interest-only periods on investment loans are usually capped at five years, after which the loan reverts to principal and interest. If you fix for five years on an interest-only basis, the revert rate at the end of that period will apply to a principal and interest calculation, which increases your repayment significantly. You need to model that step-up before committing to the loan structure, particularly if rental income alone must cover the new repayment level.

Tax Treatment of Fixed Rate Investment Loan Interest

Interest on borrowings used to acquire or hold a rental property is deductible to the extent the property is rented or held to produce assessable income. The character of the loan, fixed or variable, does not change the deductibility. However, break costs incurred when you refinance or sell before the fixed term expires are generally deductible in the year they are incurred, provided the original borrowing was used for income-producing purposes.

If you refinance an investment loan to pull out equity for private purposes, the interest on that additional borrowing is not deductible. The ATO requires you to apportion interest between the investment component and the private component. Most lenders will split the facility into two loans at the time of refinancing to simplify that record-keeping. If you are using debt recycling strategies to convert non-deductible debt into deductible debt, keep the investment loan and the recycled portion in separate accounts from the outset.

For properties acquired on or after 7:30pm AEST on 12 May 2026 that do not qualify as eligible new builds, rental losses including interest deductions are quarantined. You can carry those losses forward to offset future rental income or future residential property capital gains, but you cannot use them to reduce your salary or other non-residential income. The quarantine does not prevent you from claiming the interest deduction, it simply restricts where that deduction can be applied.

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