What borrowing capacity actually means
Borrowing capacity is the maximum amount a lender will let you borrow based on your income, expenses, debts, and deposit. Every lender runs your numbers through their own calculator, which is why you might get approved for $650,000 with one bank and $720,000 with another on identical income.
The calculation starts with your gross income, then strips away your living expenses, other loan repayments, and a buffer for rate rises. What's left is what they think you can comfortably put toward a mortgage. Lenders don't care that you rarely use your credit card or that you'll cancel Netflix once you move. They assess you at your worst-case spending, not your intentions.
Income isn't just your base salary
Most salaried workers know their base income counts, but lenders also consider overtime, bonuses, rental income, and even some government benefits if they're consistent. The catch is how they weight it. A bonus you've received for three consecutive years might be counted at 80% or 100%, but a one-off payment won't shift the dial. Rental income is typically assessed at 80% to account for vacancy and maintenance, even if your tenant hasn't missed a payment in five years.
Consider a buyer in Castle Hill earning $95,000 base salary plus a $12,000 annual bonus. One lender might add the full $12,000 to serviceability, while another only counts $9,600. That difference alone can change your borrowing capacity by $50,000 or more. If you're relying on non-salary income to hit your price range, you'll need recent tax returns, payslips showing the pattern, and sometimes a letter from your employer confirming it's ongoing.
The expenses lenders actually care about
Lenders use a benchmark called the Household Expenditure Measure (HEM) to estimate your living costs, but they don't just accept the HEM figure if your actual spending is higher. They'll take the greater of HEM or your real expenses, which they pull from your bank statements. That means three months of Uber Eats, Afterpay payments, and weekend spending all get scrutinised.
Buy Now Pay Later commitments like Afterpay, Zip, and Klarna are treated as ongoing liabilities even if your balance is zero. A $2,000 limit can reduce your borrowing capacity by $15,000 to $20,000 depending on how the lender assesses it. If you're not using it, close the account at least three months before applying for pre-approval. The same logic applies to credit cards. A $10,000 limit you never touch can cost you up to $50,000 in borrowing capacity because lenders assume you could max it out tomorrow.
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How debt-to-income ratios limit what you can borrow
From early 2025, APRA lifted restrictions on high debt-to-income lending, meaning banks no longer face strict limits on loans above six times your gross income. That doesn't mean they'll approve everyone at eight times income, but it does mean lenders have more flexibility if the rest of your application is solid. Your DTI is still calculated, and a ratio above 6:1 will attract more questions and tighter scrutiny on expenses.
If you're earning $120,000 and want to borrow $800,000, that's a DTI of 6.67. Some lenders will approve it without hesitation if your expenses are low and your deposit is 20% or more. Others will cap you at $720,000 regardless of how much you have saved. The difference isn't your income or deposit, it's lender policy. That's where a broker who knows which lender assesses higher DTI loans becomes useful.
The serviceability buffer that quietly cuts your limit
Every lender adds a buffer of 2.5% to 3.5% on top of the interest rate you'll actually pay. If the variable rate you're offered is 6.1%, the lender tests whether you could afford repayments at 8.6% or higher. That buffer is designed to protect you and the bank if rates rise, but it also shrinks what you can borrow right now.
A borrower looking at a $700,000 loan at 6.1% over 30 years would pay roughly $4,230 per month. But the lender doesn't test serviceability at $4,230. They test it at the buffered rate, which would push the repayment to around $5,100 or more. If your income and expenses don't leave enough room for that higher figure, your borrowing capacity drops even though you'll never actually pay it.
Two moves that actually increase what you can borrow
Paying down non-deductible debt has the biggest immediate impact. A $15,000 car loan with $400 monthly repayments can reduce your borrowing capacity by $80,000 or more. Clear it, and that capacity comes back. The same applies to personal loans, student debt, and even some store credit accounts that report to your credit file.
Increasing your deposit doesn't directly lift your borrowing capacity, but it opens the door to lenders with better serviceability calculators. If you're sitting at a 10% deposit and borrowing capacity is tight, getting to 15% or 20% means you can switch from a high-LVR lender to one that's more generous with income assessment. You're not earning more, but the lender treating your application differently can add $40,000 to $60,000 to what you're approved for.
Why two applicants with the same income get different answers
Lender policy varies more than most buyers realise. Some lenders assess overtime at 100%, others at 80%, and a few won't count it at all if you've been in the role for under two years. One lender might ignore your $3,000 credit card limit if the balance is zero, while another builds it into your monthly commitments at 3% of the limit regardless.
Location also plays a role, though not in the way people assume. Castle Hill postcodes sit within the Sydney metro caps for the Australian Government 5% Deposit Scheme, with a $1,500,000 property price limit. That doesn't change how much a bank will lend you, but it does mean buyers using the scheme have access to a wider range of properties without needing a 20% deposit or paying LMI. If your borrowing capacity is sitting around $650,000 and you have a 10% deposit saved, using the scheme can put you into the market faster than waiting another year to build a 20% deposit on a higher-priced property.
When a second income gets counted differently
Joint applications generally improve borrowing capacity, but not always by the amount you'd expect. If one applicant earns $110,000 and the other earns $60,000, the combined serviceability isn't just the sum of two individual applications. The lender also combines your expenses, debts, and liabilities, and some lenders apply a higher HEM figure for couples or households.
In situations where one applicant has irregular income, such as contract work or a recent job change, some lenders will exclude that income entirely if it doesn't meet their continuity requirements. That's worth knowing before you assume two incomes will automatically double your borrowing power. If you're applying jointly and one income is less secure, speak to a broker who can match you with a lender that weights both incomes more favourably.
What to do before you apply for pre-approval
Run your own numbers before a lender does. Pull three months of bank statements and add up what you're really spending. If it's more than you thought, you've got time to adjust. Close accounts you're not using, especially Buy Now Pay Later services and credit cards. Pay down small debts if you can. Even clearing a $5,000 balance can add $20,000 or more to what a lender will approve.
If your income includes overtime, bonuses, or rental income, gather the evidence now. Recent payslips, tax returns, and lease agreements all need to be current and consistent. Lenders won't give you credit for income they can't verify, and if your most recent tax return doesn't reflect what you're earning now, you'll need extra documentation to bridge the gap. If you're weighing up your home loan options or trying to understand how different loan structures affect what you can borrow, it's worth getting clarity before you start applying.
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Frequently Asked Questions
How do lenders calculate my borrowing capacity?
Lenders start with your gross income, subtract your living expenses and existing debts, then apply a serviceability buffer of 2.5% to 3.5% above the actual interest rate. What's left determines how much you can borrow.
Does closing a credit card really increase how much I can borrow?
Yes. A $10,000 credit card limit you never use can reduce your borrowing capacity by up to $50,000 because lenders assume you could max it out. Close unused accounts at least three months before applying.
Why do different lenders offer me different borrowing amounts?
Each lender has their own serviceability calculator and policies. One might count your bonus at 100%, another at 80%, and some won't count it at all if it's not guaranteed. That difference can shift your borrowing capacity by $50,000 or more.
Do Buy Now Pay Later services affect my borrowing capacity?
Yes. Even if your balance is zero, lenders treat the limit as a potential liability. A $2,000 Afterpay or Zip limit can reduce your borrowing capacity by $15,000 to $20,000.
What's a debt-to-income ratio and does it limit what I can borrow?
Your DTI is your total borrowing divided by your gross income. While APRA removed strict caps in early 2025, lenders still scrutinise ratios above 6:1 and may limit your borrowing or require stronger evidence of serviceability.
