Borrowing power vs serviceability: what banks actually check

Mortgage brokers love the phrase "borrowing power" because it sounds like a number you own. Banks use the word "serviceability" because it points at the question they actually ask: can this household keep paying the loan if rates rise and life tightens? The two concepts overlap but are not the same thing, and the gap between them is where pre-approvals collapse at the formal-application stage.

This article walks through what an Australian assessor at a major bank actually plugs into the model when your application lands on their desk in 2026.

The serviceability model in one sentence

A bank takes your assessable income, subtracts a household expense floor and your existing debt commitments, applies a regulator-mandated interest-rate stress test to the new loan, and checks that what is left is positive with a small margin. If the residual surplus passes, the loan services. If it does not, the loan is declined or shaped down.

How income is shaded

Banks do not treat all income equally. The shading depends on how stable the income source is over a credit cycle.

Salary from full-time PAYG employment is taken at 100%, provided you have cleared probation. Overtime and shift allowances are usually shaded to 80%, and in essential-services occupations (police, paramedics, nursing) some lenders accept 100% with two years of payslips. Bonuses and commissions are typically the two-year average shaded to 80%. Self-employed income is the most conservatively treated category: most lenders want two years of tax returns and the lower of the two figures, with a sanity-check against the latest BAS.

Rental income from existing investment properties is shaded to 70% or 80% by most majors, the difference covering vacancy, non-deductible costs, and the gap between gross and net rent. That 10-percentage-point spread between lenders is worth real money on a $30,000 rent roll: roughly $3,000 of assessable income either way, which translates to about $25,000 of borrowing capacity at current stress rates.

Government family benefits are accepted only where the youngest eligible child is well below the age cut-off. Share dividends and managed-fund distributions are usually shaded heavily or excluded outright. Crypto holdings, even sizeable ones, count for nothing.

The HEM floor

Every authorised deposit-taking institution uses some version of the Household Expenditure Measure as a floor on declared living expenses. HEM is published quarterly by the Melbourne Institute and segments households by location, composition, and income bracket. If your declared expenses are below HEM for your bracket, the bank substitutes the HEM number.

The implication most applicants miss is that under-declaring expenses does not buy borrowing capacity. It just gets you bumped up to the HEM floor for your bracket. Where you can move the needle is in the bracket itself: a household earning just above a HEM income threshold sits in a higher assumed-expense bucket than a household just below it. Two earners on $145,000 each may face a noticeably higher HEM than a household at $140,000 each, even though the actual lifestyle is identical.

Real declared expenses above HEM stand. If you genuinely spend $4,500 a month on living costs and HEM for your bracket is $3,800, the bank uses $4,500. Honesty is the right strategy because the bank will pull three months of transaction data and cross-check anyway, and inconsistency between declared and observed spending is a faster path to decline than an honest high number.

The APRA 3-percentage-point buffer

Since October 2021 every regulated lender has had to assess new residential loans at the contracted rate plus 3 percentage points. APRA tightened the buffer from 2.5 points to 3.0 points during the rate-cutting era of 2021 and has not relaxed it since. In a quoted-rate environment of 6.25%, the bank tests serviceability at 9.25%. The repayment that has to fit your surplus is the stressed one, not the advertised one.

On a $700,000 loan over 30 years, the gap between a 6.25% repayment ($4,310/month) and a 9.25% stressed repayment ($5,758/month) is $1,448 a month. That $1,448 of surplus is what a bank requires you to demonstrate before approving the loan. If your numbers only support the actual repayment and not the stressed one, the loan is shaped down to whatever principal does service.

The buffer applies to all your existing debts as well, not only the new one. Investors with three existing mortgages running on 2-3% honeymoon rates from 2021 are now being assessed on those same loans at 5-6% buffered, which is why the borrowing capacity of a leveraged investor has compressed faster than wage income alone would suggest. The borrowing power estimator applies the buffer to the new loan, and the mortgage calculator lets you sanity-check what the stressed repayment looks like in cash terms.

How HELP debt is treated

HELP (formerly HECS) is treated as a debt for serviceability even though the repayments are income-contingent and the balance does not appear on your credit file. Lenders look at the compulsory repayment percentage that applies to your income tier and treat it as an ongoing monthly liability for as long as a balance exists.

On $120,000 of taxable income the compulsory rate is 8%, which is $9,600 a year or $800 a month. That $800 reduces your assessable surplus dollar for dollar, and at current stress rates costs you roughly $80,000 to $90,000 of borrowing capacity. Whether to clear a HELP balance before applying for a mortgage is a genuine decision: paying off $20,000 of HELP frees up the full repayment in serviceability while only costing you $20,000 of cash. That trade-off pays back in borrowing capacity faster than most people expect.

Credit-card limits and other revolving debt

Banks assess credit cards on the limit, not the balance. A $20,000 unused card limit is treated as a roughly $600 to $760 monthly debt commitment, depending on the lender's assessment-rate policy (typically 3.0% to 3.8% of limit per month). Closing or reducing card limits before applying is one of the cheapest ways to lift serviceability, because the capacity gain is real and immediate.

Buy-now-pay-later facilities are now caught by similar treatment. A $2,000 Afterpay limit will not move the needle much, but four BNPL accounts each with $1,500 of limit will knock $20,000 to $30,000 off borrowing capacity. The fastest win on a tight application is consolidating or closing the lot a fortnight before you submit.

Debt-to-income ratio

Beyond serviceability, APRA monitors lenders on the share of new loans written at debt-to-income ratios above 6. Most majors treat DTI of 6 as a soft policy ceiling and DTI above 7 as outside appetite without strong compensating factors. A household on $200,000 of gross combined income hits the DTI 6 ceiling at $1.2M of total debt, regardless of what the serviceability calculator says about the headroom. This is a recent constraint that did not bite in the cheap-money era and now binds harder than serviceability for high-income households in expensive cities.

What this means for you

The two-step playbook in 2026 looks like this. Start with a ballpark from the borrowing power estimator to know whether you are in $500k or $900k territory. Then get formal pre-approval from at least two lenders, because the variance between policies is wide enough that the answer at one bank is not the answer at any bank.

Before you submit, do the cheap housekeeping. Cut card limits to what you actually use, close BNPL accounts, decide whether a small HELP balance is worth clearing in cash. None of these is glamorous and all of them move borrowing capacity by amounts that matter. Once you know what a lender will actually approve, the stamp duty calculator and the suburb scanner turn the loan ceiling into a realistic shortlist of postcodes and price points.

Borrowing power as a number is useful as a planning tool. The only number that closes a sale is the one a credit assessor signs off after putting your file through the model above.