Disclaimer:
This article provides general information only and does not constitute financial, legal, tax, or investment advice. Property investment involves risk. Always do your own research and seek personalised advice from qualified professionals before making investment decisions.
Key Takeaways
- A lender must assess whether required repayments are likely to be affordable without substantial hardship; its assessment method and assumptions can vary.
- There is no single public stress-test rate that applies to every lender or application; obtain the lender’s current assessment assumptions.
- Assessment assumptions can produce a different borrowing limit from a calculation based only on the current advertised repayment.
- Lenders can use different policies and evidence, but approval also depends on income, expenses, debts, security, loan purpose and applicable lending restrictions.
- Use lender calculations as an assessment, not a promise that a loan or investment will remain affordable.
Affordability assessment is one part of an investment-property mortgage application. Income, expenses, existing debt, security, loan purpose, credit information and current lender and regulatory settings can all matter.
A lender must make reasonable inquiries and be satisfied that required repayments are likely to be affordable without substantial hardship. Lenders may test higher-rate or other downside scenarios, but the method and result are lender- and application-specific.
How the Stress Test Works
A lender may use an assessment rate, floor, buffer or other servicing assumptions. Do not rely on generic figures; ask for the current basis applying to the proposed loan:
Common Stress Test Methods:
- Assessment rate or buffer: confirm the lender’s current figure and how it applies to each loan
- Floor or minimum assumption: confirm whether one applies and whether it differs by product or term
- Other assumptions: confirm repayment basis, term, recognised income, expenses, existing limits and debts
The Impact on Borrowing Capacity
An assessment-rate calculation can differ materially from the current contractual repayment. Any example depends on the loan term, repayment basis, fees and assumptions:
Example:
Assume you have $2,000 per month available for loan repayments:
- At 5% (actual rate): This services approximately $375,000 in P&I loans
- At 7% (stress test rate): This services approximately $300,000 in P&I loans
- Difference: About $75,000 less borrowing capacity due to stress test
Existing and proposed debts can affect affordability. The lender decides how it treats each balance, limit, repayment and term under its current policy.
Why the Stress Test Exists
The stress test is not designed to frustrate you. It exists for good reasons:
- Protect borrowers: Ensures you can handle rate increases without financial distress
- Financial system stability: Reduces the risk of widespread defaults if rates spike
- Regulatory requirements: Banks must demonstrate prudent lending practices
- Historical lessons: Past rate cycles have caught borrowers off guard
How Banks Apply the Test
Principal and Interest Assessment
Most banks assess all loans on a principal and interest basis for stress testing purposes, even if you have interest-only loans. This is more conservative but reflects the eventual repayment requirement.
Existing Debt Inclusion
The stress test applies to all your debt, not just the new loan. Your existing home loan, any investment loans, and other debts are all assessed at the higher rate.
Income and Rental Shading
Lenders may treat different income sources conservatively. A lender may recognise only part of expected rent and may require evidence; the percentage and treatment are lender- and property-specific.
Variations Between Banks
Different banks use different stress test parameters. These differences can significantly affect your borrowing capacity:
- Assessment rates, floors and buffers can differ and change
- Recognised income, expenses and existing-debt treatment can differ
- Treatment of existing fixed-rate loans varies
- Any policy exception is lender- and application-specific and does not guarantee approval
A regulated mortgage adviser can explain the providers and products they cover, but may not cover the whole market. Compare scope, fees, commissions, total cost and conditions; another lender is not guaranteed to approve the application.
Running Your Own Stress Test
Before applying for a loan, run your own stress test. This helps you understand your buffer and prepare for the bank's assessment.
DIY Stress Test Checklist:
- ☐ Calculate your current total loan repayments
- ☐ Model several higher-rate scenarios rather than assuming one universal buffer
- ☐ Check you could still cover all expenses with the higher payment
- ☐ Consider what would happen if a tenant left (vacancy)
- ☐ Factor in potential maintenance or emergency costs
A household scenario can expose risk but does not reproduce a lender’s assessment or predict approval. Keep finance and due-diligence conditions appropriate to the agreement and obtain legal advice before signing.
Strategies to Improve Your Position
Reduce Other Debts
Paying off credit cards, car loans, or personal loans reduces your stressed debt servicing and improves your position. Even reducing credit card limits (not just balances) helps.
Increase Income
Higher income directly improves your serviceability. This could be a pay rise, a second job, or demonstrating additional rental income from existing properties.
Choose the Right Lender
Compare written offers and assessment assumptions across lenders within the adviser’s disclosed scope. A higher borrowing limit is not by itself evidence that the loan or investment is suitable or affordable.
Structure Loans Strategically
Loan term, repayment type and extra-payment rights are contract-specific. A longer term can change periodic repayments and total interest; compare the written total cost, fees, restrictions and downside scenarios rather than assuming extra payments are always available.
When Stress Tests Change
Stress test parameters are not fixed forever. Banks adjust them based on:
- Regulatory guidance from the Reserve Bank
- Economic conditions and outlook
- Competition and market pressures
- Their own risk appetite and portfolio considerations
Changes in lender policy or regulatory settings can affect assessments, but they do not reliably predict approval or provide a basis for timing a property purchase.
The Bottom Line
The mortgage stress test is a reality of borrowing that you need to understand and work with. It will reduce your maximum borrowing capacity compared to what you might expect based on current rates, but it also provides a valuable safety check.
Model rate, vacancy, maintenance and income shocks, then compare the result with the lender’s written assessment and terms. If using an adviser, check regulatory status, provider scope, fees and commissions; do not treat maximum borrowing capacity as a target or safety guarantee.