Whatever variable rate you're actually offered on an Australian home loan, that's not the rate your borrowing capacity is tested against. APRA requires every lender to assess serviceability using either your actual rate plus a 3 percentage point buffer, or a lender-set floor — whichever is higher — meaning your real affordability ceiling is set by a rate you'll likely never pay.
How the Buffer Works
APRA's guidance, in place since late 2021, requires authorised deposit-taking institutions to test new borrowers' capacity to repay at a rate at least 3 percentage points above the loan's actual interest rate. If you're offered 6.19%, your lender must confirm you could service the loan at roughly 9.19% before approving it — a deliberately conservative test designed to absorb future rate rises and financial shocks.
Worked Example
A borrower offered 6.19% on the $520,000 loan from our Mortgage Calculator example:
| Actual Rate | Buffered Assessment Rate | |
|---|---|---|
| Rate | 6.19% | 9.19% (6.19% + 3%) |
| Monthly payment (25-yr) | ≈ $3,413 | ≈ $4,405 |
The lender isn't asking whether you can afford $3,413/month — they're confirming you could still service roughly $4,405/month before approving the $520,000 loan at all. That gap is the entire mechanism behind why headline borrowing capacity often comes in lower than a naive income-based estimate.
Common Mistakes
Buyers frequently estimate their own affordability using their actual quoted rate, then are surprised when a lender's approved amount comes in lower than expected — the buffered rate, not the advertised rate, is what determines the ceiling.
Buyers also assume the buffer is negotiable or waivable for strong applicants — it's a regulatory floor APRA applies system-wide; individual lender risk appetite can affect other parts of the assessment, but not this specific buffer requirement.
A third mistake: not accounting for how existing debts get stressed the same way. A credit card limit (even if unused) or an existing variable-rate loan gets assessed at a buffered rate too, compounding the effect on total borrowing capacity.
Where This Calculator Has Limits
It applies the standard 3% buffer, but individual lenders can and do set their own floor rates on top, which sometimes exceeds the buffered rate depending on the lender's specific risk settings — meaning actual approved amounts can vary between lenders even for identical income and debt profiles. It also can't fully model how existing credit card limits or other liabilities are individually stressed, since that varies by lender policy.
Frequently Asked Questions
Is the 3% buffer the same for every lender?
The 3-point minimum is set by APRA and applies broadly across authorised lenders, though individual lenders can apply a higher floor if their own risk policy calls for it.
Does the buffer apply to refinancing too?
Yes — refinancing to a new lender generally requires passing the same buffered serviceability test as a new purchase, which is part of why some existing borrowers find refinancing harder than their original approval was.
Can I ever borrow at the buffered rate itself?
No — the buffer is purely an assessment tool; your actual repayments are always calculated at your real contract rate, not the higher stress-tested figure.
Does a bigger deposit offset the buffer's effect?
Indirectly — a bigger deposit means a smaller loan amount, which reduces the buffered monthly payment being tested, potentially bringing an otherwise-tight application back within serviceable range.
Has the buffer level changed over time?
Yes — it moved from 2.5 to 3 percentage points in October 2021 and has stayed there since, though APRA reviews serviceability settings periodically as part of broader financial stability policy.
Related Tools
Mortgage Calculator · DTI Ratio Calculator · LMI Calculator
Educational content, not financial advice. Serviceability buffer requirements are set by APRA and can change — confirm your specific borrowing capacity with a licensed Australian mortgage broker. Written by the MortgagePro Global team.