Most property investors focus on finding the right property and the lowest interest rate — but loan structure is equally important. The way your loans are set up determines how much interest is tax-deductible, how flexible you are to sell or refinance individual properties, and whether you accidentally create tax problems that cost you thousands. Poor loan structuring is one of the most common and costly mistakes made by Australian property investors. This guide explains the key principles.
Why Does Loan Structure Matter for Investment Property Tax Deductions?
The fundamental rule of Australian tax law on investment property interest deductions is simple: interest is only deductible to the extent the borrowed funds are used for income-producing purposes. This means the purpose of the borrowing — not the security — determines deductibility.
Example 1 (correct structure): You borrow $400,000 to purchase an investment property. All $400,000 goes directly to the investment purchase. The interest on the full $400,000 is tax-deductible because the funds were used for an income-producing purpose.
Example 2 (incorrect structure): You refinance your owner-occupied home loan, increasing it from $300,000 to $500,000. You use the extra $200,000 as a deposit for an investment property. Only the interest on the $200,000 used for investment purposes is deductible — the interest on the $300,000 owner-occupied portion is not. If these are combined in a single loan account, tracking the deductible portion becomes complex.
Example 3 (common mistake): You have an investment loan of $400,000 with $50,000 in a redraw facility. You redraw $50,000 for a personal holiday. The $50,000 redrawn for personal use is no longer borrowed for an income-producing purpose — the interest on that $50,000 is not deductible. The deductible loan is now $350,000, not $400,000 — permanently, unless you repay the $50,000 specifically to the investment loan.
This is why separate loan accounts for each purpose are essential. Never mix owner-occupied and investment borrowing in the same loan account. Never use an investment loan redraw for personal purposes.
Never Redraw from an Investment Loan for Personal Use
If you redraw $20,000 from your investment loan to pay for a car or holiday, the interest on that $20,000 is no longer tax-deductible — permanently. The ATO traces the use of funds, not the security. This is one of the most common and costly mistakes investors make. Use an offset account instead of redraw for investment loans — it avoids this problem entirely because offset funds are never 'inside' the loan.
Why You Should Avoid Cross-Collateralisation
Cross-collateralisation occurs when two or more properties are used as security for a single loan (or group of loans with the same lender). This is common when you use equity in your existing home to purchase an investment property and the lender bundles everything together.
Why it is a problem:
Reduced flexibility: If you want to sell one property, refinance one loan, or move one property to a different lender, the cross-collateralised structure makes this difficult or impossible without the lender's cooperation. The lender holds security over all your properties — they may not release one without reassessing the entire portfolio.
Valuation risk: If one property declines in value, the lender may reassess the total portfolio and demand additional security, reduce your available equity, or restrict further borrowing — even if your other properties have increased in value.
Forced sale risk: In extreme circumstances (e.g., you default on one loan), the lender has security over all cross-collateralised properties and can sell any or all of them to recover the debt — not just the property associated with the defaulted loan.
Loss of negotiating power: With all your lending concentrated at one lender under cross-collateralisation, you lose the ability to shop around. Moving one loan to a competitor triggers a restructure of the entire portfolio.
The correct structure: Each property should have its own standalone loan with its own security — not linked to your other properties. If you need to access equity in Property A to fund the deposit for Property B, set up a separate equity release loan (secured against Property A only) and use those funds as the deposit. Property B then has its own separate loan secured only against Property B.
This structure gives you maximum flexibility: each property can be sold, refinanced, or moved to a different lender independently — without affecting your other investments.
Use Multiple Lenders for Maximum Flexibility
Many experienced investors deliberately use different lenders for each property. This prevents cross-collateralisation entirely, ensures each loan is independently assessed, and gives you maximum flexibility to sell, refinance, or restructure individual properties without affecting the others. Your broker can coordinate applications across multiple lenders simultaneously.
- ✓Keep each property on a separate standalone loan with its own security
- ✓Never cross-collateralise owner-occupied and investment properties
- ✓Use a separate equity release split to fund investment deposits
- ✓Each loan should be independently serviceable on its own merit
- ✓Different lenders for different properties maximises flexibility
- ✓Avoid bundling multiple properties under one lender package
Offset Accounts, Redraw Facilities, and Common Tax Traps
For investment properties, the choice between an offset account and a redraw facility has significant tax implications — unlike for owner-occupied homes where the difference is primarily about flexibility.
Offset account on an investment loan: An offset account does not change the loan balance — it simply reduces the interest charged. If you have a $400,000 investment loan with $50,000 in offset, interest is charged on $350,000. The full $400,000 loan remains in place, and if you withdraw the $50,000 from the offset for any purpose, interest reverts to being charged on $400,000 — and the full amount remains deductible because the loan purpose has not changed.
Redraw on an investment loan: Extra repayments reduce the actual loan balance. If you have a $400,000 loan and make $50,000 in extra repayments, the loan balance is now $350,000. If you then redraw $50,000 for personal use, the loan balance returns to $400,000 — BUT only $350,000 is deductible because the $50,000 was redrawn for a non-income-producing purpose. The ATO traces the use of the redrawn funds.
This distinction is critical: with an offset, you retain full flexibility. With a redraw, withdrawing funds for personal use permanently reduces the deductible portion of the loan.
Best practice for investors:
Attach the offset account to your owner-occupied loan — not your investment loan. Your owner-occupied interest is not deductible, so offsetting it saves you the most tax. Keep your investment loan balance as high as possible (every dollar of interest is deductible at your marginal tax rate).
Pay the minimum repayment on your investment loan. Direct all surplus cash to the offset account linked to your owner-occupied loan. This maximises the non-deductible interest saving while preserving the full deductible balance on the investment loan.
If you do not have an owner-occupied loan: Attach the offset to the investment loan — but treat it as a holding account for surplus cash, not a redraw substitute. Never use the offset balance to permanently reduce the investment loan principal unless your strategy is to pay down the investment loan.
The Golden Rule: Offset on Owner-Occupied, Max Deductions on Investment
Park your surplus cash in an offset account linked to your owner-occupied (non-deductible) home loan. Pay only the minimum on your investment (deductible) loan. This strategy maximises tax deductions while minimising non-deductible interest — a double benefit. If you only have investment loans, use the offset on the loan with the highest interest rate.
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About the Author
Sakib Manzoor
Senior Finance Wellness Expert
Sakib Manzoor is the founder of Secure Finance and brings extensive experience in Australian mortgage broking and financial wellness. Specialising in helping clients achieve their property finance goals through personalised strategies and expert guidance, Sakib is FBAA accredited and committed to providing clear, actionable advice. All content is written to meet Australian regulatory standards and is regularly updated to reflect current market conditions.