A pre-approval is not a guarantee.
That distinction sounds minor until you are at contract stage and the number no longer works — not because your financial position has changed, but because the assumptions built into the pre-approval were never explained to you.
Understanding what a pre-approval actually reflects, and what could cause it to shift, is one of the most practical things a buyer can know before they commit to a purchase.
What a pre-approval is — and what it isn't
A pre-approval confirms that at a specific point in time, based on the financial information you provided, a lender assessed your borrowing capacity at a particular figure.
It is a point-in-time calculation. It is not a locked position. It does not guarantee that the same figure will be supported when you submit a live application — which is a separate process, assessed against the conditions that exist at the time you apply.
The gap between those two moments is where most of the surprises happen.
How borrowing capacity is calculated
When a lender assesses your borrowing capacity, they are not simply checking whether you can afford the repayments at the interest rate being offered. They apply what is called a serviceability buffer — a rate set above the actual loan rate — to test whether you could still meet repayments if rates moved higher.
APRA requires lenders to apply a buffer of at least 3 percentage points above the rate being assessed. This is the mechanism that creates the gap between the rate on your loan and the rate your application is actually tested against.
That buffer moves with the rate environment. If rates change between when your pre-approval was issued and when you submit a live application, the assessment rate changes with them — and so does the borrowing capacity figure your pre-approval was built on.
What can cause a pre-approval to produce a different result
Several things can shift the outcome between pre-approval and live application. Most buyers are not aware of all of them.
Interest rate movements. If the lender adjusts its rates after your pre-approval is issued, the serviceability buffer applied to your application changes. A borrowing capacity figure calculated under one set of rate conditions may look different when the application is submitted weeks or months later.
Changes to your financial position. A new credit facility, a change in employment, or any reduction in income between pre-approval and application will be picked up at full assessment. Credit enquiries during a property search — multiple applications to different lenders — can also affect your credit file and the outcome.
Changes to lender policy. Lenders review their serviceability settings and credit policies periodically. A policy change after your pre-approval is issued can affect how your income or liabilities are treated when your application is assessed in full.
The property itself. A pre-approval covers your borrowing capacity as a borrower. It does not pre-approve a specific property. Once a property is identified, the lender will assess it separately — its type, location, construction, and title structure can all affect whether the loan proceeds on the terms the pre-approval indicated.
Why the contract stage is where this matters most
Pre-approvals create confidence, which is appropriate — they confirm that your position supported a particular borrowing figure at a given time. The problem is when that confidence is treated as certainty.
Unconditional contracts are binding. A buyer who signs at the top of their approved amount — based on a pre-approval issued several months earlier, without revisiting the underlying figures — may find that the assessment position has shifted by the time the live application is submitted.
The rate environment may have moved. Their financial position may have changed. Lender policy may have been updated. Any one of these factors can produce a materially different outcome at application stage.
This is not a failure of the pre-approval process. It is a function of how assessments work: they reflect the conditions in place at the time they are run, not a fixed position that holds indefinitely.
What to confirm before you sign
The pre-approval figure is a starting point for understanding your position — not a guarantee that holds regardless of when or where you apply it.
Before signing a contract, it is worth confirming whether your pre-approval is still current and whether the rate environment has shifted since it was issued. Whether anything in your financial position has changed — new liabilities, credit enquiries, or variation in income. And whether the property you are considering has any characteristics that might affect how the lender assesses it at full application.
These are not complex questions. But they are the ones that tend to go unasked — and they are the ones that change the outcome when they do.
Understanding how your pre-approval was calculated, not just the number it produced, is what puts a buyer in a genuinely informed position before a contract is signed.