What Is Serviceability in Personal Loans? The Full Formula Explained

Serviceability is the word that decides almost every personal loan outcome, and almost nobody asks what it actually means until after they've been knocked back. It isn't your credit score, and it isn't your income on its own — it's what's left over once everything else is accounted for.

The short answer

Serviceability is a lender's test of whether your income — after living costs, rent, and existing debts — leaves enough to cover a new loan repayment. It's calculated as a residual: what's left over each month. If that number is zero or higher, you pass. If it's negative, the application fails, regardless of your credit score.

Key takeaway: Serviceability = Net income − HEM (living costs) − rent/mortgage − existing debts − the new loan repayment. Passing means the result is $0 or more. A genuinely comfortable pass needs at least $200/month left over.

The formula lenders actually run

Residual = Net Monthly Income − HEM − New Loan Repayment − Rent or Mortgage − Credit Card Obligation (3.5% of total limits) − BNPL Repayments − Existing Personal Loan Repayments − Existing Car Loan Repayments

Pass: residual ≥ $0. Comfortable pass: residual ≥ $200/month — this is the bar used to calculate a "safe" borrowing amount, rather than just a technical pass.

HEM — the floor lenders use instead of your actual expenses

HEM (Household Expenditure Measure) is a standardised, conservative estimate of basic living costs. Lenders use it instead of asking exactly what you spend — even if your real expenses are lower, the HEM figure is still deducted. It's a floor, not a reflection of your actual budget.

The base figure is the same whether you're single or in a couple, but the two tables diverge sharply from the first dependant. A single parent's HEM jumps by $1,300 with just one child, because that household is covering a dependant's costs on one income. A couple absorbs each additional child more gradually, since the base living costs are already split two ways.

A worked example — a clean pass

Take someone with:

• Net monthly income: $4,800
• 0 dependants → HEM: $2,500/month
• Rent: $1,400/month
• No other debts
• Credit card limit: $10,000 → assessed at $350/month (3.5%)
• Proposed new loan repayment: $550/month

Residual = $4,800 − $2,500 − $1,400 − $350 − $550 = $0

Exactly zero. It technically passes — affordability requires a residual of $0 or more — but there's nothing left over. A single unused credit card ate the entire margin.

A worked example — where it fails

Now take someone with a similar income but one dependant and an existing car loan:

• Net monthly income: $4,200
• 1 dependant, single → HEM: $3,000/month
• Rent: $1,600/month
• Existing car loan repayment: $380/month
• Credit card limit: $15,000 → assessed at $525/month (3.5%)
• Proposed new loan repayment: $500/month

Residual = $4,200 − $3,000 − $1,600 − $380 − $525 − $500 = −$1,805

This application fails serviceability decisively, and no amount of a strong credit score changes that outcome — the formula doesn't ask what your score is. The two biggest levers pulling this residual negative are the HEM step-up from having a dependant, and the unused portion of the $15,000 credit card limit. Either one coming down would materially change the result.

Serviceability vs DTI — two different tests

Serviceability and DTI are checked separately, and a strong result on one doesn't guarantee the other. DTI looks at what percentage of your gross income is committed to debt. Serviceability looks at whether there's genuinely enough cash left over each month, after rent and living costs too. Both have to pass — see Debt-to-income ratio explained for the full DTI breakdown.

What lenders actually look at

HEM is a floor, not your budget

Spending less than HEM doesn't help your position — lenders don't ask what you actually spend. Someone who genuinely lives on $1,200 a month is still assessed at the full HEM figure for their household size, because the whole point of a standardised floor is that it can't be talked down.

Employment type changes how income is calculated

PAYG income uses your gross annual salary. Casual income is averaged over your last 3 months of deposits. Self-employed income is averaged over your last 2 years of ATO-assessed income. This means two applicants with identical current earnings can have different "net monthly income" figures in this formula, purely because of how their employment type is averaged.

The $200 "comfortable" buffer

This is what's used to calculate a T2 "safe" borrowing amount — a genuine pass with room to move, rather than a residual that scrapes in at zero. The clean-pass example above technically clears serviceability, but at $0 residual it wouldn't be returned as a "safe" amount by the calculator — it's a pass on paper with no buffer against a bill you didn't budget for.

The broker amount is a ceiling, not a guarantee

A specialist may be able to access up to 15% more than your safe amount, depending on your full profile. That uplift reflects a broker's ability to place an application with a lender whose specific policies suit your situation — it isn't a different formula, just a wider pool of lenders to try.

How to improve your serviceability position

• Reduce credit card limits you don't need — this is often the single biggest lever, since limits count whether you use the card or not.
• Pay down or consolidate loans with the highest repayments first — see Debt consolidation loans: how lenders actually assess them.
• Consider a smaller loan amount or a longer term to lower the proposed repayment.
• Run the numbers in the T2 Borrowing Capacity Calculator before you apply — it shows both your residual and your safe borrowing amount.

Serviceability is the test that catches people off guard, because it has nothing to do with credit history. If you want to see your own residual before you apply, the T2 Borrowing Capacity Calculator runs this exact formula, including your rent, HEM, and credit card limits.