How Lenders Calculate Your Borrowing Capacity
Lenders assess your borrowing capacity by calculating your net monthly income, subtracting your existing commitments and living expenses, then determining how much you can service at an interest rate typically 3.0 percentage points above the actual loan rate. That buffer protects both you and the lender if rates rise.
Consider a buyer in Falcon earning $95,000 per year with a partner earning $68,000. Their combined gross income is $163,000, which translates to roughly $10,800 per month after tax. They have a car loan with $420 monthly repayments, one credit card with a $6,000 limit, and their living expenses for a household of two adults and one child are estimated by the lender at around $3,200 per month. The lender assesses the credit card at its limit multiplied by 3% per month, adding another $180 to their commitments. After subtracting $3,800 in total commitments and living expenses from their net income, they have $7,000 available to service a home loan. At a serviceability assessment rate of around 9.0%, that $7,000 monthly serviceability gives them a borrowing capacity of approximately $730,000, well within reach of Falcon's median house price of $775,500.
Your borrowing capacity is not the same as your deposit-adjusted purchase price. If this couple has saved a 10% deposit plus costs, their total purchase range sits closer to $670,000 once stamp duty concessions and the deposit are factored in, even though their serviceability supports a loan of $730,000. The distinction matters because buyers often assume they can afford more than their deposit will allow, or conversely, that a modest income rules them out when in fact their low commitments give them strong capacity.
The 3.0 Percentage Point Serviceability Buffer
APRA requires all authorised deposit-taking institutions to assess new borrowers' capacity to service a home loan at an interest rate at least 3.0 percentage points above the loan product rate. If the variable rate on offer is 6.2%, the lender tests your capacity at 9.2%. That buffer has been in place since October 2021 and remains the current standard.
For a buyer borrowing $650,000 over 30 years, the actual monthly repayment at 6.2% is around $4,000. At the assessed rate of 9.2%, the repayment used in the serviceability calculation is closer to $5,350. The lender needs to see that your income, after all expenses and commitments, can cover that higher figure. This protects you from overcommitting if rates move higher during the life of your loan, and it protects the lender from lending beyond what you can realistically afford.
The buffer applies to new borrowers only. Existing borrowers are not reassessed under the buffer when their fixed rate expires or when they refinance with the same lender, though switching lenders will trigger a fresh serviceability assessment under the current buffer.
Income Sources Lenders Accept
Lenders typically accept income from salary and wages, rental income from investment properties, and certain government benefits, though the treatment of each varies depending on the lender and the stability of the income source. Permanent full-time and part-time employment income is accepted at 100% of its verified amount. Casual income may be accepted at 80% after a minimum employment period, usually 6 to 12 months with the same employer. Rental income is usually assessed at 80% of the lease amount to account for vacancy and maintenance costs.
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Self-employed income requires at least two years of tax returns in most cases, and lenders assess the net profit after business expenses and tax. Overtime, bonuses and commissions are treated conservatively, some lenders average them over two years, others exclude them entirely unless they are guaranteed. Centrelink payments such as Family Tax Benefit and Parenting Payment are accepted by most lenders, though the percentage assessed varies. Child support received is often accepted at 100% if it is court-ordered and has been received consistently.
The structure of your income affects not just how much you can borrow but which lender will offer the most competitive outcome. A borrower with 20% casual income may receive a stronger outcome from a lender that assesses casual loading at 100% rather than 80%, even if that lender's interest rate is marginally higher.
Commitments That Reduce Your Capacity
Every ongoing financial commitment reduces the amount you can borrow. Car loans, personal loans, and buy now pay later accounts are assessed at their actual monthly repayment. Credit cards are assessed at 3% of the card limit per month, regardless of how much you owe or whether you pay the balance in full. A $10,000 credit card limit reduces your borrowing capacity by the equivalent of a $300 monthly commitment, which over 30 years equates to roughly $50,000 in lost borrowing power.
If you are paying school fees, childcare, or private health insurance, some lenders will include those in their living expense assessment, others will add them as a separate line. HECS-HELP debt does not appear as a monthly repayment on your credit file, but lenders include it by calculating a repayment threshold based on your income. Once your income exceeds the compulsory repayment threshold, the lender reduces your net income by the percentage withheld, which in turn reduces your serviceability.
Closing unused credit accounts before applying for a home loan can materially increase your borrowing capacity. Even a card you have not used in two years is still assessed at 3% of its limit. Paying down or closing a personal loan early has the same effect. The month before you apply is too late to make these changes, lenders require at least one statement cycle showing the account as closed or the balance reduced.
Living Expenses and the Household Expenditure Measure
Lenders use one of two methods to assess your living expenses. They either apply the Household Expenditure Measure, a benchmark based on household size and income published by the financial regulator, or they assess your actual declared expenses, whichever is higher. The HEM is not negotiable. A single person with no dependents will be assessed at a minimum of around $1,800 to $2,200 per month depending on the lender and income bracket. A couple with two children will be assessed at closer to $3,800 to $4,500 per month.
If your actual spending is lower than the HEM, the lender still uses the HEM. If your actual spending is higher, the lender uses your declared figure and may request bank statements to verify it. Declared expenses include groceries, transport, utilities, insurance, clothing, medical costs, entertainment, subscriptions, and education costs. Some lenders exclude childcare from this category and assess it separately.
Living expenses vary by postcode in some serviceability models, though not all lenders apply geographic adjustments. A household in a metropolitan area may be assessed at a higher HEM than the same household in a regional centre, though the difference is typically modest, around 5% to 10%. Falcon falls within the Mandurah region, which is treated as part of the broader Peel region for most lender serviceability purposes.
Debt-to-Income Lending Limits
APRA activated a debt-to-income lending limit on 27 November 2025, effective from 1 February 2026, restricting authorised deposit-taking institutions to lending no more than 20% of new owner-occupier loans and 20% of new investor loans to borrowers with a total DTI ratio of six times or greater. The limit applies separately to owner-occupier and investor lending portfolios and applies to new lending only.
For a buyer with a household income of $140,000, a DTI of six times equates to total borrowing of $840,000. If that buyer already has $120,000 owing on an investment property, their maximum new borrowing under the DTI limit would be $720,000, assuming the lender has capacity within its 20% allocation. In practice, most lenders manage their portfolio to stay within the limit by tightening serviceability policy slightly before they hit the threshold, rather than declining applications outright.
Non-bank lenders are not subject to the DTI limit, which can give them a serviceability advantage for borrowers with high income and high debt. The limit does not apply to bridging loans for owner-occupiers or to loans for the purchase or construction of new dwellings. First home buyers purchasing new builds or using schemes such as the Australian Government 5% Deposit Scheme are not affected by the DTI restriction in most cases, as new dwelling purchases are carved out.
How Loan Structure Affects Borrowing Capacity
The loan structure you choose affects your serviceability assessment. Principal and interest loans are assessed at the repayment required to pay down the loan over the chosen term, typically 30 years. Interest-only loans are assessed at the interest-only repayment for the interest-only period, then at the principal and interest repayment required to repay the remaining balance over the remaining term. That creates a higher serviceability hurdle for interest-only loans, even though the actual repayment during the interest-only period is lower.
A $600,000 loan at 6.5% over 30 years on principal and interest has a monthly repayment of around $3,790. The same loan on a five-year interest-only period followed by 25 years of principal and interest is assessed at the $3,250 interest-only repayment for five years, then at roughly $4,100 per month for the remaining term. The lender assesses serviceability at the higher figure, which reduces your borrowing capacity even though you are paying less for the first five years.
Split loans are assessed as the weighted average of the fixed and variable portions. If you fix 60% of a $700,000 loan at 5.9% and leave 40% variable at 6.3%, the lender assesses the fixed portion at 8.9% and the variable portion at 9.3%, then calculates your serviceability at the blended rate. Offset accounts do not change the serviceability assessment, though they reduce the actual interest you pay once the loan settles.
Improving Your Borrowing Capacity Before You Apply
Borrowing capacity is not static. Paying down debt, closing unused credit accounts, increasing your income, or reducing discretionary spending all improve your serviceability and increase the amount you can borrow. The most immediate change comes from closing credit cards and paying out small personal loans. A buyer with a $15,000 credit card limit and a $8,000 personal loan with $320 monthly repayments is losing roughly $100,000 in borrowing capacity. Clearing both commitments one month before applying adds that capacity back.
Increasing your deposit does not directly increase your borrowing capacity, but it does increase your purchase price range and may reduce or eliminate the cost of lenders mortgage insurance, which in turn reduces the loan amount required. A buyer with a 15% deposit avoids LMI on some lender products, reducing the amount they need to borrow by several thousand dollars compared to a 10% deposit with LMI capitalised into the loan.
If your income has increased recently, update your payslips before applying. Lenders assess your income based on your most recent payslip and may average the last two or three. A pay rise that occurred two months ago but has not yet been captured in your application will reduce your assessed income. Similarly, if you have switched from casual to permanent employment, wait until the change is reflected on your payslip before applying, as permanent income is assessed at 100% rather than 80%.
Why Borrowing Capacity Varies Between Lenders
No two lenders assess serviceability identically. One lender may assess rental income at 80% of the verified rent, another at 75%. One lender may add a fixed buffer to your living expenses, another may rely entirely on the HEM. One lender may exclude overtime unless it has been received for two years, another may include it after six months. These differences compound, and a borrower who is declined by one lender may be approved by another without any change to their financial position.
In one scenario, a buyer earning $110,000 per year applies to a major bank and is offered a maximum loan of $580,000. The same buyer applies to a different lender through a broker and is offered $640,000. The difference comes down to how each lender treats a $12,000 per year car allowance. The first lender excludes it entirely, the second lender includes it at 80% after verifying that it has been received consistently for 12 months. That $9,600 difference in assessed income translates to $60,000 in additional borrowing capacity.
Working with a mortgage broker gives you access to serviceability calculators across multiple lenders before you apply. That means you know which lender will deliver the strongest outcome for your specific income and commitment profile, rather than applying to one lender and hoping for the right result. Borrowing capacity is one of the most lender-specific variables in the home loan process, and choosing the right lender is often more valuable than securing a marginally lower interest rate.
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Frequently Asked Questions
How do lenders calculate borrowing capacity?
Lenders calculate your net monthly income, subtract existing commitments and living expenses, then determine how much you can service at an interest rate 3.0 percentage points above the actual loan rate. The serviceability buffer protects both you and the lender if rates rise.
Why does a credit card limit reduce my borrowing capacity even if I pay it off in full?
Lenders assess credit cards at 3% of the card limit per month, regardless of your balance or repayment history. A $10,000 limit reduces your borrowing capacity by roughly $50,000 over a 30-year loan term.
What is the debt-to-income lending limit?
From 1 February 2026, banks can lend no more than 20% of new owner-occupier loans to borrowers with a total debt-to-income ratio of six times or greater. The limit applies separately to owner-occupier and investor lending and does not apply to non-bank lenders.
Can I increase my borrowing capacity before applying?
Yes. Paying down debt, closing unused credit accounts, increasing your income, or switching from casual to permanent employment all improve your serviceability. The most immediate change comes from closing credit cards and paying out small personal loans.
Why does borrowing capacity vary between lenders?
Lenders assess income, expenses, and commitments differently. One lender may accept 80% of rental income while another accepts 75%. One may include overtime after six months, another may exclude it entirely. These differences compound and can result in borrowing capacity variations of $50,000 or more between lenders.
