When prospective property buyers evaluate their home loan affordability, they typically calculate repayments using the actual market interest rate—say, 6.20%. However, when authorized deposit-taking institutions (ADIs) assess that same borrower, they calculate repayments at an artificial stress test rate approaching 9.20%.
The Mechanics of the 3.0% APRA Buffer
Under prudential guidelines established by the Australian Prudential Regulation Authority (APRA), banks must assess a borrower’s repayment capability at the higher of either:
- The contract interest rate plus a minimum serviceability buffer of 3.0 percentage points (300 basis points); or
- The lender’s internal floor rate (historically around 5.25% to 5.50%).
This macroprudential lever was designed to ensure mortgage holders can absorb future monetary policy tightening without defaulting. However, every 100-basis-point increase in the assessment interest rate reduces a typical household’s maximum borrowing capacity by approximately 8% to 10%.
Household Expenditure Measure (HEM) and Credit Limits
In conjunction with the serviceability buffer, lenders apply the Household Expenditure Measure (HEM) benchmark. If your declared living expenses are lower than the HEM baseline for your income and family composition, the lender replaces your declared numbers with the higher HEM figure, further compressing borrowing limits.
Unused credit card limits are also assessed at approximately 3.8% per month. A dormant credit card with a $20,000 limit reduces borrowing power by roughly $80,000 to $100,000 under the APRA stress test. Cancelling unneeded credit facilities prior to application is an immediate lever to restore capacity.
Non-Bank Lenders and Tier-2 Discrepancies
Crucially, APRA prudential standards formally apply to ADIs (major banks and mutual banks). Non-bank lenders and private securitized funders operate under ASIC consumer credit rules and occasionally retain greater flexibility regarding buffers, particularly for refinancing like-for-like debt.
To understand how banking facility features help manage interest costs, read our analysis on Offset Accounts vs. Redraw Facilities, or review our guide on Pre-Approval Pitfalls at Auction.
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