A "mortgage prisoner" is a borrower whose existing loan is fine (they are making the payments), but who cannot refinance to a cheaper rate because their borrowing capacity under current serviceability rules is lower than their current loan balance. The new lender, applying the APRA 3 per cent buffer to today's rates, says no. The current lender is not required to re-test and so the borrower stays put on a back-book rate that may be 50-100 basis points above what a new applicant would get.
Industry estimates published by RFI in May 2026 put the trapped-borrower cohort at around 320,000 households, or roughly 7 per cent of the variable owner-occupier book. The number rose sharply after the May 6 cash-rate hike to 4.35 per cent because the assessment rate moved from 8.74 per cent to 8.99 per cent, tipping a fresh tranche of borrowers from "marginal" into "trapped".
How a borrower becomes a prisoner
The mechanic is straightforward. You borrowed $720,000 in early 2022 at a 2.79 per cent fixed rate, which rolled in 2025 to a 5.79 per cent variable. You can afford the repayments. Your income has risen and the household budget is tight but functioning. Today you go to your broker and ask: can I refinance to that 5.79 per cent rate I just saw advertised at another bank? The broker runs the numbers at 8.79 per cent assessed (current rate plus 3 per cent buffer), and the new lender comes back saying you can borrow $640,000. You owe $695,000. The application fails.
If the 9-per-cent-ish assessment rate is unfamiliar, our explainer on the mortgage stress test (see /resources/mortgage-stress-test-explained) walks through how it is built and why a refinance application can fail even when the current loan is being paid on time.
The same household, if they applied as new buyers today at their current income for a new $695,000 loan, would also fail. But they already hold the loan. The original lender continues to charge them whatever rate they choose to apply to that loan, and the borrower has no exit.
Who is most at risk
- Borrowers who came off ultra-cheap 2021-2022 fixed rates (the "fixed rate cliff" cohort) and now hold variable rates above 5.5 per cent.
- High-LVR refinancers: borrowers who bought with a 5-10 per cent deposit and have not yet built equity buffer.
- Single-income households where serviceability is tighter under any buffered test.
- Borrowers with new dependants since the original loan was written. HEM increases per child reduce assessed capacity.
- Self-employed borrowers, where assessed income is typically the lower of two years' accountant-certified earnings.
Path one: same-lender rate review
The first and lowest-effort path is to ask your existing lender for a rate review or "retention" offer. Big-four lenders typically have a retention desk that operates outside the front-book pricing system. The retention discount can range from 20 to 80 basis points on existing variable rates. A 50-basis-point cut on a $700,000 loan is roughly $290 a month: meaningful, immediate, no application form, no credit check, no buffer test.
The catch: the lender will give you the smallest cut they think will keep you. If you cannot credibly threaten to leave (because you are a prisoner), you may not get the best offer. The trick is to get a written quote from another lender as ammunition even if you cannot actually use it. Brokers do this routinely.
Path two: like-for-like refinance under streamlined assessment
APRA carved out an exception in 2023 (APG 223 update) that lets lenders refinance an existing borrower at a like-for-like loan size without the 3 per cent buffer being applied at full strength. The carve-out is not automatic. Each lender chooses whether to use it, and the credit policies of the participating lenders vary. As at May 2026, ANZ, Westpac, Macquarie, Bank of Queensland and a handful of non-bank lenders offer streamlined refinance products that prisoners can sometimes access. Loan-to-value ratio needs to be reasonable (typically under 80 per cent), repayment history needs to be clean, and the new loan cannot exceed the old loan balance.
Brokers on a wide panel know which lenders accept these applications and which are paying lip service. A broker who only deals with two or three lenders may not be able to find you a streamlined refinance path even when one exists.
Path three: switch to interest-only temporarily
Some lenders will assess affordability at the interest-only payment rather than the principal-and-interest payment, which lowers the assessed monthly commitment and may bring a borrower over the line. This is a workable bridging move for a borrower who expects income to rise within 1-3 years (return to work after parental leave, expected promotion, completed study debt). The risks are real: you stop building equity during the IO period, and you face a higher P&I payment when the IO term expires. Use carefully.
Path four: structural changes to the loan
Three structural moves can change the borrowing capacity calculation: extending the loan term back to 30 years (lowers assessed monthly repayment), consolidating credit-card and BNPL limits into a single product (cuts the assessed liability), and switching the income earner on the loan if one partner's income has materially shifted. None of these are silver bullets but in combination they can shift a marginal borrower over the threshold.
Worth watching: the APRA review
APRA opened a consultation on 22 May 2026 on the 3 per cent buffer itself. If the regulator moves the buffer lower or to a dynamic setting, the prisoner cohort shrinks materially overnight. The realistic earliest implementation date is October-November 2026 and lender pass-through can lag by another month or two. Most of the current trapped borrowers cannot afford to wait six months on speculation, but the policy direction is worth tracking.