Serviceability and What Lenders Actually Check

When you apply for a home loan, the lender is trying to answer one question: can you afford the repayments?

That question gets answered through a serviceability assessment. It's a calculation that takes your income, subtracts your expenses and commitments, then applies a buffer to see whether you can still meet the repayments if rates move higher. The assessment determines how much you can borrow, and whether your application proceeds or stalls.

How Lenders Calculate Your Income

Lenders assess your income differently depending on how you're paid. A salaried medical professional working in Parramatta with a base salary and regular shift allowances will usually have their income verified using payslips and an employer letter. Most lenders accept 100% of base salary and between 80% and 100% of regular allowances that have been consistent over at least three months. Overtime is typically assessed at 80% of the average over six to twelve months.

For self-employed buyers, including specialists and GPs operating through a practice or trust structure, lenders generally require two years of financials and tax returns. They calculate serviceability using your net profit plus any add-backs such as depreciation, but may reduce that figure if the most recent year shows a decline in income. Some lenders will accept a single year of returns if accompanied by an accountant's declaration, though this is less common for larger loan amounts.

Rental income from an investment property is usually assessed at 80% of the gross rent to allow for vacancy and maintenance costs. If you're purchasing an investment property and the lease has not yet commenced, some lenders will accept a signed lease agreement or a rental appraisal from a licensed agent.

The Expenses Side of the Calculation

Your committed monthly expenses are just as important as your income. Lenders will include your existing home loan repayments, personal loan commitments, car finance, and credit card limits. They assess credit cards at the full limit, not your current balance. If you have a $10,000 limit and a zero balance, the lender will still include a minimum monthly repayment of around 3% to 3.5% of that limit in the serviceability calculation.

This catches a lot of buyers off guard. In our experience, closing unused credit accounts or reducing limits before applying can improve borrowing capacity significantly, particularly for buyers with multiple cards or store accounts.

Lenders also apply what's called the Household Expenditure Measure, or HEM. It's a benchmark figure for living costs based on household size and income, published by the Melbourne Institute. Some lenders use your declared living expenses if they exceed HEM, while others will default to HEM regardless of what you declare. For a single professional earning $120,000 in Parramatta, HEM might assume monthly living costs of around $2,200 to $2,500 depending on the lender's version of the index. A couple with one child will see that figure increase to somewhere between $3,200 and $3,800.

The Interest Rate Buffer and Why It Matters

Every lender must assess your ability to service the loan at a rate higher than the one you'll actually pay. The buffer is set by the Australian Prudential Regulation Authority at a minimum of 3.0 percentage points above the loan product rate. If you're applying for a variable rate loan at 6.2%, the lender will assess whether you can afford repayments at 9.2%.

Consider a buyer purchasing in Parramatta who needs to borrow $650,000. At a product rate of 6.2%, the monthly repayment on a principal and interest loan over 30 years is around $4,000. At the buffered rate of 9.2%, the repayment jumps to around $5,350. The lender's serviceability calculation is based on the higher figure. If your income minus expenses minus HEM doesn't leave enough room for that $5,350 repayment, the loan amount will need to come down or the application won't proceed.

The buffer applies to all new home loan applications lodged with an authorised deposit-taking institution. It doesn't apply to existing borrowers who are making additional repayments or switching products with the same lender, though policy varies by institution.

Debt-to-Income Limits From February 2026

From 1 February 2026, APRA introduced a lending limit that restricts the share of loans a bank can write to borrowers with a debt-to-income ratio of six times or more. Each lender can write up to 20% of new owner-occupier loans and 20% of new investor loans above that threshold.

If your total borrowings, including the new loan, equal six times your gross annual income or more, your application may be declined or require a larger deposit even if it otherwise meets serviceability. A medical registrar earning $130,000 and applying for a loan of $780,000 sits exactly at the six times threshold. If that same buyer also has a $40,000 car loan, their total debt rises to $820,000 and the ratio moves above six. Some lenders will still approve the application within their allowable portion, while others may decline or ask for the car loan to be cleared first.

The limit applies separately to owner-occupied home loans and investment loans, and doesn't apply to bridging finance or loans for the purchase or construction of new dwellings.

What Happens When Serviceability Comes Up Short

If the initial assessment shows you can't service the amount you need to borrow, there are a few ways to adjust the structure. Increasing the deposit reduces the loan amount and can bring the repayments within serviceability. Adding a co-borrower, such as a spouse or partner, increases the household income and changes the calculation. Paying out or reducing other debts, particularly high-interest personal loans or credit card limits, frees up monthly cashflow.

Switching to an interest-only loan structure lowers the monthly repayment during the interest-only period and may help the application meet serviceability, though the overall cost of the loan increases and the balance doesn't reduce until you revert to principal and interest. Some lenders also allow you to extend the loan term beyond 30 years if you're under a certain age, which reduces the monthly repayment and improves the serviceability outcome.

We regularly see buyers in Parramatta, particularly those working at Westmead Hospital or in the health precinct around Jeffery House, who assume their income alone will be enough to borrow what they need. Income is only half the picture. A surgeon earning $300,000 with three investment properties, two car loans and $80,000 in credit limits may have less borrowing capacity than a nurse earning $90,000 with no debt.

How a Broker Structures the Application to Fit Lender Policy

Different lenders assess income and expenses in different ways. One lender might accept 100% of overtime while another caps it at 80%. One might assess credit cards at 3% of the limit while another uses 3.8%. One lender's HEM figure might be $400 higher per month than another's. Those differences compound quickly when you're borrowing in the mid-six figures.

A mortgage broker will model your serviceability across multiple lenders before lodging, then match your income structure and debt profile to the lender whose policy gives you the highest borrowing capacity. If you're self-employed, that might mean targeting a lender that allows single-year financials or accepts a higher percentage of net profit. If you have a company car or salary packaging arrangements common among hospital staff in Parramatta, it means finding a lender that treats those benefits favourably in the income calculation.

That's not something you can replicate by going direct to your existing bank. You'll get one answer, and it might not be the right one.

If you're looking at properties in Parramatta or preparing to apply for pre-approval, call one of our team or book an appointment at a time that works for you. We'll run the serviceability calculation upfront so you know exactly where you stand before you start looking.

Frequently Asked Questions