How Lenders Calculate Your Borrowing Capacity
Borrowing capacity is the maximum loan amount a lender will approve based on your income, expenses, debts, and the lender's own serviceability test. Each lender applies a different formula, which means the figure you receive from one institution can vary significantly from another.
Most lenders start with your gross income and then subtract your living expenses, existing debt repayments, and a buffer to account for future interest rate rises. The remaining amount is assessed against their serviceability criteria to determine how much you can afford to borrow. This calculation happens before any discussion of deposit size or property type.
Consider a buyer who earns $110,000 annually with no dependents and a $600 monthly car loan repayment. One lender might assess their borrowing capacity at $580,000, while another could approve up to $620,000 based on how they treat living expenses and the serviceability buffer they apply. The difference isn't always obvious until you test the application across multiple lenders.
Income Assessment Beyond Your Payslip
Lenders assess your income based on how stable and verifiable it is. A full-time salary with two years of payslips is straightforward, but other income types require more documentation and may be shaded differently in the calculation.
Bonus income, commission, and overtime are typically averaged over the past two years, and some lenders will only count 80% of that average. Rental income from an investment property is usually assessed at 80% of the actual rent to account for vacancy and maintenance costs. If you're self-employed, most lenders require two years of tax returns and will use your taxable income after deductions, which can reduce your borrowing power compared to a PAYG employee on the same gross figure.
In Doncaster, where many buyers work in professional services or run their own businesses, the way lenders treat different income types can directly impact affordability. A self-employed physiotherapist earning $140,000 in gross revenue might only have $95,000 in taxable income after deductions, and that lower figure is what the lender uses. This is where understanding lender policy becomes critical, particularly if you're applying for a home loan with variable income streams.
The Serviceability Buffer and Why It Changes Your Ceiling
The serviceability buffer is an additional interest rate margin that lenders add to the current variable rate when testing whether you can afford the repayments. This buffer is not the rate you pay, but the rate the lender uses to stress-test your loan.
Most lenders apply a buffer of 3%, meaning if the current variable interest rate is 6.5%, they assess your repayments at 9.5%. This ensures you can still afford the loan if rates rise. Some lenders use a lower buffer, which can increase your borrowing capacity without changing your actual repayments.
A buyer looking at properties in Doncaster's established residential areas near Ruffey Lake Park or Westfield Doncaster might find that switching to a lender with a 2.5% buffer instead of 3% increases their maximum loan amount by $30,000 to $40,000. That difference can be the margin between securing a property or being outbid.
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Declared Living Expenses vs Household Expenditure Measure
Lenders assess your living expenses using one of two methods: the Household Expenditure Measure (HEM) or your declared expenses, whichever is higher. The HEM is a standardised estimate based on household size and income level, published by the Melbourne Institute.
If you declare $2,800 per month in living expenses but the HEM for your household type is $3,200, the lender will use the higher figure. This can reduce your borrowing capacity even if your actual spending is lower. Some lenders allow you to use declared expenses if they're substantiated with bank statements, which can work in your favour if you live conservatively.
For buyers in Doncaster, where private school fees and childcare costs are common, declared expenses often exceed the HEM. A family with two children in private education might have $4,500 per month in committed living costs, which will directly reduce the loan amount they can service. This is where the choice of lender matters, because not all institutions assess schooling costs the same way.
Existing Debts and How They're Factored In
Every existing debt you carry reduces your borrowing capacity. Lenders don't just subtract your actual monthly repayment, they often apply a minimum repayment percentage to the outstanding balance, particularly for credit cards and personal loans.
A credit card with a $15,000 limit might only have a $200 monthly repayment, but the lender will assess it at 3% of the limit, which equates to $450 per month. Even if you pay the balance in full each month, the limit itself reduces what you can borrow. Closing unused credit accounts before you apply for a home loan can materially increase your serviceability.
Car loans, personal loans, and Buy Now Pay Later accounts are also included. A $30,000 car loan with $700 monthly repayments will reduce your maximum loan amount by approximately $140,000, depending on the lender's calculation method. If you're planning to purchase in Doncaster and your borrowing capacity is already tight, paying down or consolidating existing debts before applying can be more effective than increasing your deposit.
Loan to Value Ratio and Its Indirect Effect on Capacity
The loan to value ratio (LVR) is the size of your loan compared to the property's value. While LVR doesn't directly change your borrowing capacity, it does affect whether Lenders Mortgage Insurance (LMI) is required and whether the lender will approve the loan at all.
If your borrowing capacity allows you to borrow $650,000 but you only have a 10% deposit on a property valued at $700,000, you'll need to borrow at 92.8% LVR. Most lenders cap residential lending at 95% LVR for owner-occupied purchases, and some reduce serviceability at higher LVRs due to the additional risk. LMI becomes payable above 80% LVR, and while this cost can be capitalised into the loan, it increases the total amount you're borrowing, which can push you beyond your assessed capacity.
In a scenario where a buyer has been approved for $650,000 but needs $665,000 after LMI is added to the loan, the application may fail at the final assessment stage even though the initial capacity figure seemed adequate. This is why working through the full calculation, including LMI, before making an offer is critical.
How Lender Policy Differences Create Opportunity
Every lender has a different credit policy, and those differences can result in significantly different borrowing capacity outcomes. Some lenders don't count rental income from boarders or Airbnb, while others will assess up to 80% of it. Some lenders shade overtime income more conservatively, while others accept 100% of it if it's been consistent for two years.
One major lender might decline a self-employed applicant with one year of trading history, while another will consider the application if there's prior industry experience. A buyer in Doncaster who works in a specialist field such as consulting or allied health may have strong income but limited financials if they've recently transitioned to self-employment. Testing that application across lenders with varied policy settings can uncover an approval that wouldn't exist with a single submission.
This is also where home loan pre-approval becomes valuable. Pre-approval not only confirms your maximum loan amount, but it locks in the lender's assessment of your financial position for a set period, giving you certainty when you're ready to make an offer on a property near the Doncaster Manningham border or further east toward Donvale.
Why Your Borrowing Capacity Isn't Static
Your borrowing capacity can change between the time you're pre-approved and the time you submit a full application. If interest rates rise, lenders adjust their serviceability calculations, which reduces the maximum loan amount. If your income drops or you take on new debt, your capacity also falls.
Some buyers assume that once they're pre-approved, the figure is guaranteed. It's not. Pre-approval is conditional on your financial circumstances remaining unchanged and the lender's credit policy staying the same. If you apply for a credit card, finance a car, or reduce your working hours between pre-approval and settlement, the lender will reassess and may reduce or withdraw the approval.
In our experience, buyers who keep their financial position stable and avoid taking on new commitments during the purchase process avoid unnecessary complications. If you're planning to upgrade your car or consolidate debt, do it before you apply for pre-approval, not after.
Call one of our team or book an appointment at a time that works for you. We'll assess your income, expenses, and existing commitments across multiple lenders to identify which one will give you the highest borrowing capacity based on your specific financial profile.
Frequently Asked Questions
How do lenders calculate my borrowing capacity?
Lenders start with your gross income and subtract living expenses, existing debt repayments, and a buffer to account for future rate rises. The remaining amount is assessed against their serviceability criteria to determine the maximum loan amount they'll approve.
Why does my borrowing capacity differ between lenders?
Each lender applies a different serviceability buffer, treats income types differently, and assesses living expenses using varied methods. These policy differences can result in borrowing capacity variations of $40,000 or more between institutions.
Does my credit card limit affect how much I can borrow?
Yes. Lenders typically assess credit cards at 3% of the limit per month, even if you pay the balance in full. A $15,000 limit can reduce your borrowing capacity by approximately $90,000, which is why closing unused accounts before applying can increase what you're approved for.
Can I use rental income to increase my borrowing capacity?
Most lenders will assess rental income at 80% of the actual rent to account for vacancy and maintenance. This applies to investment properties you already own, and the shaded income is added to your gross income in the serviceability calculation.
What is the serviceability buffer and how does it affect my loan?
The serviceability buffer is an additional interest rate margin, usually around 3%, that lenders add to the current rate when testing if you can afford the repayments. It's not the rate you pay, but it determines the maximum loan amount you can service.
