Serviceability buffer (assessment rate)
What is a serviceability buffer, and why is a loan tested at a higher rate?
ONE OF 366 TERMS · FREE · NO SIGNUP
BY MICHAEL SHANG · SIXTEEN YEARS IN COMMERCIAL BANKING · UPDATED
// THE SHORT ANSWER
A serviceability buffer is the margin a lender adds to a loan's actual interest rate to set the rate, often called the assessment or test rate, at which it checks that the borrower can afford the repayments. In Australia the prudential regulator requires new home loans to be assessed at least 3 percentage points above the product rate; New Zealand banks set their own test rates; UK lenders must consider likely rate rises under conduct rules, a separate stress test having been withdrawn in 2022. Business lenders apply the same idea when they test cover at a sensitised rate.
BASIS Practitioner judgment from sixteen years in commercial banking, set out in How Bankers Think (Highbank Press, 2026). Every borrower on this site is a composite constructed for teaching, not a client. The market is mid-market commercial lending as practised in New Zealand and Australia; where a convention differs elsewhere, the page says so.
// WHAT IT IS NOT
Serviceability is the question of whether the borrower can pay; the buffer is the extra rate the lender adds when it asks that question.
// WORKED IN
// NEXT TO IT
// SUBSCRIBE
The Lab.
One case file and one question, in your inbox every Tuesday morning, New Zealand time. The senior banker's read opens only after you answer.
FREE WITH IT · THREE PDFS
An interview case, an annotated credit paper, and a one-page loan application sheet.
No spam. Unsubscribe anytime. Educational content only.