Australia’s interest-only lending landscape has shifted into its most consequential phase since APRA’s 2017 macroprudential crackdown. The 2020-21 vintage of five-year interest-only investment loans, written at fixed rates below 2.5 per cent, is now maturing into a very different world: the RBA cash rate target sits at 4.10 per cent as of February 2025, and standard variable investment IO rates routinely breach 6.5 per cent. For the borrower who borrowed $800,000 in March 2020 on a 2.49 per cent five-year IO term, the monthly interest bill was $1,660. That same loan, resetting to principal and interest at 6.55 per cent over a 25‑year remaining term, produces a monthly repayment of approximately $5,430 — a 227 per cent increase that no rental yield can easily absorb. The sheer scale of these resets, concentrated through 2025, is pressuring the refinancing system at a moment when serviceability buffers remain elevated and many lenders are cautious about extending interest-only periods without a full reassessment. At the same time, the removal of APRA’s hard interest‑only cap in 2018 has allowed credit to flow back into the segment, but only for borrowers who can meet a patchwork of lender-imposed DTI ceilings, LVR haircuts, and stricter income verification. This article examines what those policies mean for investors today, how major and non-bank lenders are pricing and underwriting IO loans, and where the material risks lie when the interest‑only term ends.
How Lenders Price Investment Interest-Only Loans in 2025
Variable-Rate IO: Spreads, LVR Tiers and Margins
Investment interest‑only lending is no longer priced at the wafer‑thin margins of the pre‑2022 cycle, but margin compression has returned selectively. In March 2025, the big four banks advertise packaged investment variable IO reference rates between 6.85 per cent and 7.05 per cent, yet actual negotiated rates for high‑quality borrowers with a loan‑to‑value ratio of 70 per cent or below commonly land in the 6.15‑6.40 per cent range. Non‑bank lenders, funded via warehouse lines and securitisation, have pushed that lower: Athena’s straight‑up variable IO investment rate was 6.19 per cent in February 2025, and Macquarie was offering 6.24 per cent for loans with LVR ≤70 per cent and an offset account. The cost of money matters here. The RBA’s February 2025 decision to cut the cash rate 25 basis points gave ADIs room to trim, but bank funding costs tied to the three‑month bank bill swap rate have not fallen in lockstep, keeping the net interest margin on investment IO books under pressure.
LVR bands directly dictate price. Most lenders now bake a “risk fee” into the interest rate for IO loans above 70 per cent LVR. At ANZ, for example, an investment IO loan with an LVR of 80 per cent requires a 15‑basis‑point loading on the negotiated rate, while CBA applies a tiered margin: loans at 70‑80 per cent LVR attract a premium of 10‑25 basis points depending on the industry of the borrower and whether rental income is verified via a current lease. The pricing message is clear: if an investor cannot bring equity of at least 30 per cent, the loan is treated as a higher‑risk exposure and priced accordingly.
Fixed-Period Interest-Only: Three- and Five-Year Terms
Fixed‑rate IO terms for investors have rebounded from the nadir of mid‑2023, but the discount versus variable is thin. As of early March 2025, three‑year fixed IO rates for investment loans sit near 5.99‑6.14 per cent for borrowers with clean credit and LVR ≤70 per cent; five‑year fixed IO sits at 6.29‑6.49 per cent. The narrow spread reflects the market’s expectation of further RBA easing through 2025‑26, which banks have already priced into the variable curve. Investors who lock in a five‑year fixed IO today are effectively paying a small premium to hedge against the risk that rate cuts stall or that their personal serviceability deteriorates during the term.
Non-Bank Tension in the Segment
Non‑banks have re‑entered the investment IO space aggressively over the past 12 months, but they are playing a narrower corridor. While a major bank may entertain an investment IO loan up to 90 per cent LVR with lenders mortgage insurance, most non‑banks cap IO LVR at 80 per cent, and several — including Pepper Money and Liberty — impose a hard maximum loan size of $1.5 million for IO. The trade‑off is speed and servicing leniency for self‑employed borrowers: non‑banks routinely assess investment IO serviceability using an interest‑rate add‑on of only 1.0‑1.5 percentage points above the product rate, versus the 3.0‑percentage‑point buffer still applied by ADIs for most new‑to‑bank business. This difference alone can keep a borrower in the IO market when a major bank would decline them.
The Policy Tangle: LVR, DTI and the Extension Trap
Major Bank Caps on Investment Interest-Only
Each of the big four operates a slate of overlays that narrow the path to approval. As of March 2025, CBA will not write new investment IO loans above 80 per cent LVR without a significant servicing surplus and an LMI waiver from a substantial deposit; Westpac’s hard limit is identical, though it permits 85 per cent LVR for existing customers refinancing internally. NAB maintains a blanket DTI hard cap of 7 times for all investor lending, while ANZ hard‑caps investment IO advances at 6.5 times DTI. These DTI limits are absolute: a borrower with an annual gross rental income of $100,000 and a PAYG salary of $120,000 cannot breach $1.54 million in total debt at NAB, even if the surplus rental income covers the expected repayment.
Interest-Only Extension and Re‑IO Policies
The quiet danger for investors lies in IO extension policies, which have hardened. When a five‑year investment IO period expires, the loan automatically converts to a principal‑and‑interest repayment schedule based on the remaining term, without a new credit assessment — but if the borrower wants to extend the IO term for a further period, they must pass a full serviceability test at the current assessment rate. That test is far harder than the one they passed in 2020. For a $700,000 residual loan, the difference between an assessment at a 2.5 per cent buffer (as was common pre-2021) and the current 3.0 per cent buffer is roughly $17,500 of extra annual servicing income required. Many investors simply cannot show that income growth, triggering a forced P&I repayment that may not be supported by the property’s cash flow.
Some lenders offer a “re‑IO” pathway for existing customers who do not meet the full buffer. Macquarie, for instance, allows an internal re‑IO request to be assessed at the product rate plus 1.0 per cent for borrowers with a perfect three‑year repayment history and a DTI below 6. However, this is a policy exception, not a published offering, and can be withdrawn without notice. Investors relying on it should treat it as temporary relief, not a structural solution.
Non-Bank Flexibility Comes With a Price
Non‑bank lenders have built a niche around more flexible IO extension criteria, but the pricing gap has widened. A non‑bank IO loan extended for three years at the lender’s discretion may carry a rate 30‑40 basis points above the headline variable rate, plus a $395 extension fee. For a $1 million loan, that equates to an additional $3,000‑$4,000 in annual interest. Investors must weigh that cost against the alternative of triggering a distressed sale if forced onto P&I.
Serviceability and the Refinancing Cliff
The 3 Per Cent Buffer and Its Refinancing Carve-Out
APRA’s October 2021 letter to ADIs required a minimum serviceability buffer of 3.0 percentage points over the product rate for all new residential mortgage lending, a sharp increase from the previous 2.5 per cent floor. That buffer remains in place for new-to‑bank investment IO borrowers, compressing borrowing power even as rates begin to fall. However, APRA’s letter of 24 July 2024 introduced a critical exception: for a borrower refinancing from another ADI, lenders may assess serviceability using a 1.0 percentage point buffer provided the borrower meets strict criteria — no arrears, same loan purpose, same loan-to‑valuation ratio, and a satisfactory credit history over the prior 12 months.
This “refinancing safety valve” is precisely engineered to prevent the IO reset cliff from turning into a systemic forced‑sale event. An investor holding a $900,000 loan at 6.5 per cent would need to demonstrate the capacity to meet repayments at 9.5 per cent (buffer not applied to actual repayments but to the serviceability calculation) under the standard 3.0 per cent rule, but at just 7.5 per cent under the refinancing carve‑out. For an average full‑time income household, the difference can restore $150,000‑$200,000 of borrowing headroom, allowing them to refinance from a major bank to a competitor offering a fresh IO term.
Interest Deductibility and the Tax Tail
Investors who treat interest only as a tax strategy must track the ATO’s recent tightening. The ATO ruled in June 2023 that interest on any redraw from an investment loan used for private purposes — even if later repaid — may be apportioned and partly non‑deductible. More pointedly, the Tax Office’s rental property data‑matching program, renewed in February 2025, cross‑references loan statements with rental income schedules, making it inadvisable to claim interest deductions on a loan that has been partially re‑contaminated by mixed‑use redraws. For IO investors, the cleanest path remains a separate, untouched offset account rather than a redraw facility, but not all lenders offer an offset on IO investment loans (NAB’s base IO product omits it; CBA’s “Extra Home Loan” includes it at a 0.10 per cent premium).
Payment-Shock Mathematics at Reset
A precise example underscores the cliff. A $750,000 interest‑only loan fixed at 2.29 per cent expiring in April 2025 converts to an indexed variable rate of 6.45 per cent. The interest‑only payment rises from $1,431 per month to $4,031 per month. On conversion to P&I over the remaining 25 years, the monthly payment becomes $5,038. At the property level, if the gross rental yield is 3.8 per cent on a market value of $950,000, the monthly rent is $3,008 — leaving a negative monthly cash flow of $2,030 before allowing for rates, insurance and property management. Even with depreciation benefits that reduce taxable income, the after‑tax cash‑flow hole often exceeds $1,500 per month. Investors without a liquid cash buffer are forced to sell or to accept a non‑bank bridging loan at a higher rate, further eroding equity.
Bridging and Construction: The Collateral Use of Interest-Only
Bridging Loans: IO as a Short‑Term Bridge
Investors using a bridging loan while selling one property and buying another usually pay interest‑only during the bridging term, with the lender capitalising the interest. As of March 2025, major bank bridging rates for investment property range from 6.70 per cent to 7.30 per cent, and the maximum bridging period is typically six months for a non‑committed sale and 12 months for a committed sale with an unconditional contract. Because interest is capitalised, the peak debt at the end of the bridge can exceed the origination loan by 3‑4 per cent. For a $500,000 bridging loan, that’s an extra $15,000‑$20,000 that must be cleared by the sale proceeds. Investors who over‑estimate the sale price of the exiting property or under‑estimate the time to sell can face a capitalised loan that cannot be fully discharged, forcing P&I conversion or a forced sale. Lenders, mindful of this, now re‑assess the exit property’s value at the halfway point of a non‑committed bridge, using a discounted “kerb‑side” valuation that typically comes in 10‑15 per cent below a full valuation. The gap must be covered by the borrower’s equity or the bridge will be called.
Construction Loans: Progressive Drawdowns at Interest‑Only
Construction loans for investment builds are structured as interest‑only during the build period, with interest calculated on each progress drawdown. The attraction is minimal holding cost while the asset generates no rental income. However, LVR restrictions are tighter: most lenders cap investment construction LVR at 80 per cent, and the interest‑only construction term is limited to 12‑18 months. At the end of construction, the loan must convert to either an investment P&I or an investment IO loan, requiring a full serviceability assessment at the prevailing buffer. Builds that run over time and budget — a common scenario — can leave an investor exposed when the builder’s contract price has increased mid‑project and the lender’s end‑build re‑valuation falls short of the total drawn. Investors must have a contingency equity injection ready if the final drawdown pushes LVR above the lender’s approved ceiling, which is typically 80 per cent; a single‑point LVR breach can trigger a demand for a $15,000‑$25,000 lump sum payment before the final progress payment is released.
Five Steps for Investors Holding Interest-Only Debt Now
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Stress‑test your reset date before the bank does. Model the monthly payment on P&I at a rate 1.5 percentage points above your current variable rate, and test it against your property’s net rental income plus your available household cash flow. If the shortfall exceeds 20 per cent of your monthly non‑rental income, start building a dedicated cash buffer immediately.
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Engineer a serviceability snapshot before requesting an extension. Gather two years of tax returns, a current tenancy agreement, and a pay‑slip. Approach a mortgage broker to run a desktop serviceability assessment under both the 3.0‑percent‑buffer and the 1.0‑percent refinancing‑carve‑out scenarios. If you meet the 1.0 per cent test but not the 3.0 per cent test, map the specific non‑bank and second‑tier lenders accepting refinancers under the carve‑out rather than attempting an internal extension with your current bank.
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Isolate your tax deductibility chain. Do not redraw from an investment IO loan for any purpose, even temporarily. Use an offset account if your product permits it, or hold a separate transaction account. If your loan has been contaminated by past private redraws, request a split‑loan restructure from your lender that separates the investment portion and the private portion into distinct sub‑accounts, with deductibility attached only to the clean investment sub‑loan.
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Treat five‑year fixed IO as a tactical hedge, not a yield play. Locking in a fixed IO rate at 6.29 per cent for five years costs roughly 15 basis points more than floating in March 2025. That premium buys certainty on the largest line item in your investment equation. If your employment or income stream is volatile — commission‑based, contract‑based, or tied to a single industry — the premium is justifiable. For dual‑income PAYG households with stable jobs, the flexibility of a variable IO loan with offset may be cheaper and safer.
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Before a bridging or construction IO commitment, underwrite the exit yourself. For a bridging loan, obtain two independent agent appraisals and value your exit property at the lower of the two; for a construction loan, add 10 per cent to the builder’s fixed‑price contract and check that the land‑value component plus the inflated contract does not breach the lender’s capped LVR. Keep a signed cash‑equity letter from your bank confirming you have unencumbered funds available if the end‑build valuation falls short.