What Are the Cash Flow Rules for Investment Loans?

Lenders assess investment loan applications differently to owner-occupied home loans because rental income can be used to service the debt. However, banks typically discount rental income by 20% to account for vacancy periods and maintenance costs, which means your borrowing capacity depends on both your salary and the property's earning potential after that reduction. The repayment structure you choose, whether interest-only or principal and interest, directly affects your monthly cash flow and how much tax you can claim.

How Lenders Calculate Rental Income in Servicing Assessments

When you apply for an investment loan, the lender adds 80% of the expected rental income to your other income sources, then subtracts all your expenses and existing debt commitments. The 20% reduction accounts for vacancy rate risk and ongoing costs, even if you have a tenant in place. If the property is already tenanted, the lender will use the current lease amount. If it's a proposed purchase, they typically use a rental estimate from a licensed valuer or real estate agent familiar with the area.

Consider a buyer purchasing a two-bedroom apartment near Fitzroy Gardens in East Melbourne. The property is expected to rent for $650 per week, or roughly $2,817 per month. The lender will assess serviceability using $2,253 per month in rental income after applying the 20% reduction. If the buyer earns $110,000 per year and has no other debt, the lender combines their net salary with the adjusted rental income to determine how much they can borrow. The structure matters because an interest-only loan on a $600,000 borrowing at a 6.5% assessment rate costs approximately $3,250 per month, while a principal and interest loan at the same rate costs closer to $3,800. The interest-only option improves cash flow by around $550 per month, which can be the difference between approval and refusal when serviceability is tight.

Once the loan settles, the buyer's actual cash flow depends on the gap between rental income and loan repayments, plus all other property expenses. In this scenario, if the buyer chose interest-only repayments at a lower actual rate of 6.2%, the monthly repayment drops to approximately $3,100. With rental income of $2,817 and monthly costs including body corporate fees of $400, insurance of $100, and rates of $150, the property runs at a monthly shortfall of around $933. That shortfall is claimable against other income under current negative gearing rules, reducing the buyer's taxable income and generating a tax benefit. For someone on a marginal tax rate of 37%, the after-tax cost of that shortfall is closer to $588 per month.

Interest-Only Versus Principal and Interest Repayment Structures

Interest-only investment loans allow you to pay only the interest component for a set period, typically between one and five years. Principal and interest loans require you to repay both the interest and a portion of the loan amount each month, which reduces the loan balance over time but increases the repayment amount.

Investors often choose interest-only repayments to maximise cash flow and tax deductions in the early years of ownership. Because interest is a claimable expense but principal repayments are not, an interest-only structure increases the amount you can claim each year. It also frees up cash to cover other property costs, reinvest in additional properties, or manage personal expenses. At the end of the interest-only period, the loan typically reverts to principal and interest unless you apply to extend the interest-only term. Lenders may allow one or two extensions depending on your equity position and loan to value ratio, but most require the loan to revert within 10 years.

Principal and interest repayments build equity faster and reduce the total interest paid over the life of the loan. This structure suits investors who prioritise debt reduction over cash flow, or those nearing retirement who want to own the property outright. It also improves your equity position, which can help if you plan to leverage equity for future purchases. The trade-off is higher monthly repayments and lower tax deductions, which may not align with a property investment strategy focused on portfolio growth in the short to medium term.

What Happens When Rental Income Drops or Vacancy Extends

If your tenant leaves and the property remains vacant for several weeks, you still need to cover the full loan repayment and all other costs from your own income. Lenders account for this risk during the application process by reducing the rental income in their serviceability calculations, but a prolonged vacancy can strain cash flow if you have not set aside a buffer.

Investors with multiple properties or those holding high loan to value ratio loans are most exposed to vacancy risk. A property in East Melbourne typically experiences lower vacancy periods than outer suburbs due to proximity to the CBD, public transport along Wellington Parade and Punt Road, and demand from professionals and students. However, if the property is vacant for two months, you lose approximately $5,634 in rental income while still paying the loan, body corporate, and other fixed costs. Setting aside a cash reserve equivalent to three to six months of repayments provides a cushion to manage these periods without needing to access credit or sell the property under pressure.

How Recent Policy Changes Affect Investment Loan Cash Flow

From 1 July 2027, negative gearing deductions on established residential properties purchased after 12 May 2026 will only be claimable against rental income or capital gains from residential property, not against wage income. If you bought an investment property in East Melbourne before Budget night in May 2026, your existing arrangements remain unchanged. If you purchase after that date, any net rental loss can still be carried forward to offset future property income, but the immediate tax benefit against your salary disappears.

This change directly affects cash flow for investors who rely on tax refunds to cover the shortfall between rental income and property costs. In the earlier example, the buyer with a monthly shortfall of $933 currently receives a tax benefit of around $345 per month through reduced PAYG withholding or an end-of-year refund. Under the new rules, that benefit is deferred until the property generates a profit or is sold. The buyer would need to fund the full $933 shortfall from after-tax income each month, which increases the required cash flow buffer and may reduce borrowing capacity if lenders adjust their serviceability models to reflect the policy shift.

Investors considering new builds still have the option to choose between the 50% capital gains tax discount or cost base indexation when they eventually sell, and negative gearing remains fully available for new construction. This creates a structural incentive to focus on newly constructed apartments and townhouses rather than established stock if tax efficiency and cash flow are priorities.

Using Offset Accounts and Redraw to Manage Investment Loan Cash Flow

An offset account linked to your investment loan reduces the interest charged each day based on the balance held in the account, but it does not reduce the amount of interest you can claim as a tax deduction. If you have $20,000 sitting in an offset account against a $600,000 investment loan, you only pay interest on $580,000, but your claimable interest expense is calculated on the full $600,000 if the funds in the offset are genuinely available for investment purposes. This distinction matters because mixing personal and investment funds can complicate your tax position.

Redraw facilities allow you to access extra repayments you have made above the minimum required amount. However, if you make principal repayments on an investment loan and later redraw those funds for personal use, the interest on the redrawn amount is not claimable. Investors who want to maintain full tax deductibility should avoid making extra repayments on investment loans and instead direct surplus cash to an offset account or a separate loan structure. This preserves the deductibility of all interest on the investment loan and keeps personal and investment borrowing separate.

Structuring Multiple Investment Loans Across a Portfolio

As your portfolio grows, cash flow management becomes more complex. Each property has its own loan, rental income stream, and cost structure, and the combined position determines whether your portfolio is positively or negatively geared overall. Investors often use a mix of interest-only and principal and interest loans across different properties to balance cash flow, equity growth, and tax outcomes.

For instance, an investor with three properties might hold two on interest-only terms to maximise cash flow and tax deductions, while directing extra repayments to the third property on a principal and interest loan to build equity for the next purchase. This approach maintains flexibility and ensures that at least one property is reducing in debt, which can improve serviceability when applying for additional investment loan products. Lenders assess your entire portfolio when calculating how much more you can borrow, so managing cash flow across multiple properties directly affects your ability to access investment loan options for future acquisitions.

Call one of our team or book an appointment at a time that works for you to review your current investment loan structure and discuss how recent policy changes affect your cash flow and borrowing capacity.

Frequently Asked Questions