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You’ve identified that something went wrong. The solicitor missed the deadline. The doctor didn’t pick it up in time. The financial adviser put you in something entirely unsuitable. You know there was a failure — and you’ve probably been told, at some point, that it didn’t matter. That you would have lost anyway. That the outcome was always going to be the same.
That argument has a name in law. It’s the causation defence. And it’s the single most common reason professional negligence claims are contested — not because the professional didn’t make a mistake, but because they’re arguing their mistake didn’t cause your loss.
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Causation is the legal link between a professional’s failure and the loss you suffered. It answers the question: did their breach actually cause what happened to you, or would you have ended up in the same position regardless? Without establishing that link, even a clear and provable failure to meet the expected standard will not be enough to succeed in a claim.
The starting point in almost every professional negligence claim is what lawyers call the “but for” test. The question is straightforward: but for the professional’s breach, would you have suffered the loss?
If the answer is yes — the loss would have happened anyway — causation fails. If the answer is no — the loss would not have occurred without the breach — causation is established.
This test is now codified in statute across Australia. Section 5D of the Civil Liability Act 2002 (NSW) sets out the framework: factual causation must be established first, and then the court considers whether it’s appropriate for the scope of the professional’s liability to extend to the loss in question. Equivalent provisions apply in every other state and territory.
A solicitor fails to file your proceedings before the limitation period expires. The claim is permanently barred. But for that failure, you would have had your day in court. The loss — your extinguished right to pursue the case — flows directly from the missed deadline.
Factual causation is straightforward.
A financial adviser recommends a high-risk investment without disclosing the risks. The question here isn’t just whether they breached their duty — it’s whether the type of loss you suffered falls within the scope of what they should be held responsible. Courts look at the nature of the advice and whether the loss is genuinely connected to that failure.
This is where most claimants hit a wall. The professional — or more commonly, their insurer — doesn’t necessarily deny the mistake. Instead, they argue the mistake didn’t matter. Common lines of defence include:
— “You would have suffered the same loss regardless of the advice we gave”
— “The market conditions / prognosis / outcome were always going to produce this result”
— “You made your own decision — we can’t be held responsible for the outcome”
— “Multiple professionals gave the same advice
— it was consistent with standard practice”
Each of these is designed to sever the causal link between the breach and your loss. And each of them can be tested and, in many cases, dismantled with the right evidence. Your legal team’s job is to establish the counterfactual — what would have happened if the professional had done their job properly — and to build the evidence that supports it.
Causation plays out differently depending on the profession and the nature of the failure. Here is how courts approach it across the most common claim types.
Missed limitation periods are the clearest case. The opportunity to litigate is gone. The causal link between the solicitor’s failure and the client’s loss is direct. Causation also arises in conveyancing errors, incorrect settlement advice, and failures to advise on rights under a contract — each requiring a careful analysis of what the client would have done differently with correct advice.
Causation in medical cases is often the most contested. Courts have long recognised that the strict “but for” test can produce unfair results where multiple factors — some within and some outside the practitioner’s control — contributed to the outcome. The High Court’s decision in Chappel v Hart [1998] HCA 55 confirmed that where a professional’s breach materially contributed to the risk of harm that eventuated, causation can be established. Medical negligence claims require expert evidence — but complex is not the same as impossible.
Causation in financial advice cases frequently involves scope of liability arguments. The question is not just whether the adviser got it wrong, but whether the specific type of loss suffered — a market movement, an investment collapse, a tax liability — falls within the class of risk the adviser’s duty was meant to protect against.
Incorrect advice that triggers an ATO audit, penalties, or missed tax concessions raises causation questions around what the client would have done with accurate advice, and what the financial position would have been. The counterfactual is key.
The foundational professional negligence case in Australian law. The High Court held that a surgeon who failed to warn a patient of a risk of blindness in her other eye was liable when that risk materialised. The case established the standard by which courts assess whether a professional’s failure to advise caused a foreseeable harm — the patient’s right to make an informed decision was central to causation.
The most important Australian authority on causation in medical negligence. The High Court confirmed that where a professional’s breach materially contributed to the risk that caused the harm, causation can be established. It moved beyond the rigid “but for” test to address situations where multiple factors — including the patient’s own vulnerability — contributed to the outcome.
The High Court reaffirmed the “but for” test as the primary causation standard in Australian negligence law. Factual causation requires proof that the defendant’s negligence was a necessary condition of the harm. The case serves as an important anchor for the statutory causation framework that now applies across Australian states.
Causation isn’t asserted — it’s built. The evidence your legal team will look for includes:
Particularly in medical and engineering cases, an independent expert assesses what a competent professional should have done and what difference it would have made.
Advice documents, correspondence, instructions, contracts, and file notes that establish what the professional did and didn’t do.
Evidence of what you would have done if given correct advice. In financial advice cases, this often involves establishing the alternative investments you would have chosen.
Establishing the precise point at which the breach occurred and the chain of events that followed.
What a competent practitioner in the same field would have done differently, and why the outcome would have been different as a result.
Act before time runs out.
Professional negligence claims must generally be commenced within 3 years of the date you became aware — or reasonably should have become aware — of the negligence. This timeframe varies by state: NSW, QLD, SA, ACT, and NT apply a 3-year discovery period; VIC, WA, and TAS allow up to 6 years for general claims. Missing this deadline can permanently extinguish your right to claim. If you are unsure whether your limitation period is still open, contact our team for a free assessment as soon as possible.
Yes — and this is worth understanding before you assess your claim. Where a professional’s breach was only one of several contributing factors, courts may apportion the loss.
If you are found to have contributed to the damage yourself — by ignoring advice, failing to act on information you had, or taking on a risk you understood — that can reduce the compensation awarded, even where the professional was clearly at fault. This is called contributory negligence. It doesn’t necessarily kill a claim. But it does affect the outcome.
The same applies where causation is partial — where the professional’s failure made your position worse, but you were already carrying some level of risk or loss. Courts can and do award compensation for the portion of loss attributable to the breach, even where the total picture is complicated.
Causation is the most technically demanding element of a professional negligence claim. It’s where insurers focus their defence. It’s where cases are won and lost. If you’re asking yourself whether the professional’s failure actually caused your loss — that’s exactly the question we’re here to help you answer. Our team works through the evidence, assesses the causal link, and gives you an honest view of where you stand.
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The “but for” test asks whether, but for the professional’s breach, you would have suffered the loss you did. If the answer is no — the loss would not have occurred without the breach — factual causation is established. It’s the starting point for causation analysis under the Civil Liability Acts across all Australian states and territories, though courts recognise it doesn’t resolve every situation on its own.
Possibly, yes. Where the professional’s breach contributed to your loss alongside other factors, courts can apportion liability. You may recover compensation for the portion of loss directly attributable to the breach, even if other contributing factors are also in play. This is assessed on the specific facts of each case.
Medical causation often requires independent expert evidence — a specialist in the relevant field who can assess what a competent practitioner should have done and what difference it would have made to your outcome. Where multiple factors contributed to the harm, the material contribution principle established in Chappel v Hart may allow causation to be established even without strict “but for” proof.
Yes — and they frequently do. This is one of the most common defences in professional negligence claims. The argument is that the outcome would have been the same regardless of the breach. Your legal team’s job is to build the counterfactual evidence that challenges this — demonstrating what would have happened with proper advice or treatment.
They are separate elements of a claim. Breach of duty is the failure to meet the expected standard — what the professional did or didn’t do. Causation is about whether that failure actually caused your loss. A professional can clearly breach their duty of care and still successfully defend a claim by arguing that the breach made no difference to the outcome. Both elements must be established for a claim to succeed.
Our goal is to help people in the best way possible. this is a basic principle in every case and cause for success. contact us today for a free consultation.
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