ACC Treatment Injury: What Counts, What Gets Declined, What It Pays
On average a third of treatment injury claims are declined each year, and almost two thirds of those declines come down to one thing: no evidence of a physical injury (ACC, Treatment Injury Claim Lodgement Guide, ACC7972, March 2019, retrieved 20 August 2026). In the most recent year ACC has published in detail, 2019/20, it made cover decisions on 16,604 treatment injury claims and accepted 11,285 (ACC, *Supporting Treatment Safety 2021*, July 2021, retrieved 20 August 2026).
There is no separate treatment injury payout scale. An accepted treatment injury claim gets the same entitlements as any other ACC claim, and it also closes the door on suing anyone. Both of those are worth understanding before you lodge.
What is a treatment injury under the Accident Compensation Act?
A treatment injury is a personal injury suffered by someone seeking or receiving treatment from one or more registered health professionals, caused by that treatment, and which is not a necessary part or ordinary consequence of the treatment, taking into account the person's underlying health condition and the clinical knowledge at the time (Accident Compensation Act 2001, s32(1), retrieved 20 August 2026).
Three tests, all of which have to be met. ACC's own guidance puts them in the same order: an injury has occurred that resulted in physical harm or damage, the injury was caused by treatment, and the injury is not a necessary part or ordinary consequence of the treatment (ACC lodgement guide, retrieved 20 August 2026).
The word doing the most work is "treatment", and the Act defines it far more widely than most people expect. For the purpose of deciding whether a treatment injury has occurred, treatment includes a diagnosis, a decision on what treatment to provide including a decision not to provide it, a failure to provide treatment or to provide it in a timely manner, obtaining or failing to obtain informed consent, the provision of prophylaxis, and the failure of any equipment, device, implant or prosthesis used in the treatment process (s33(1), retrieved 20 August 2026). A missed diagnosis and a delayed operation are treatment. So is a support system such as a booking process that directly supports the treatment.
Cover extends outward in one narrow case: if you suffer an infection that is a treatment injury and pass it directly to your spouse or partner, your child, or another third party, that person has cover too (s32(7), retrieved 20 August 2026).
How the 2005 test differs from medical misadventure
The category called medical misadventure applied to injuries before 1 July 2005. Section 32 was substituted on that date by section 13 of the Injury Prevention, Rehabilitation, and Compensation Amendment Act (No 2) 2005, and the Act still carries a section dealing with claims for medical misadventure before that date (s34, retrieved 20 August 2026).
Medical misadventure meant personal injury caused by medical error or medical mishap. Medical error meant the failure of a registered health professional to observe a standard of care and skill reasonably to be expected in the circumstances. Medical mishap meant an adverse consequence of properly given treatment that was both severe and rare, where severe meant death, more than 14 days as a hospital inpatient, or significant disability lasting more than 28 days in total, and rare meant the consequence would not occur in more than 1% of cases in which that treatment is given (Accident Insurance Act 1998, ss35 to 37, retrieved 20 August 2026).
| Medical misadventure, before 1 July 2005 | Treatment injury, from 1 July 2005 | |
|---|---|---|
| Route to cover | Medical error or medical mishap | A single test in s32 |
| Fault required | Yes, for the medical error limb | No |
| Severity threshold | Yes, for the mishap limb: death, more than 14 days as an inpatient, or significant disability over 28 days | None |
| Rarity threshold | Yes, for the mishap limb: not more than 1% of cases | None |
| Main exclusion | Neither limb made out | Wholly or substantially caused by the underlying health condition, or a necessary part or ordinary consequence of the treatment |
Sources: Accident Insurance Act 1998, ss35 to 37 for the medical misadventure definitions, and Accident Compensation Act 2001, s32 for the current test (both retrieved 20 August 2026). One honest caveat on the left-hand column: legislation.govt.nz does not serve a pre-2005 version of the 2001 Act, so the wording above is taken from the 1998 Act definitions that the 2001 Act carried forward until 1 July 2005.
Read the middle three rows together. The old test asked either whether someone was at fault or whether the outcome cleared two numeric hurdles. The current test asks neither. It asks what caused the injury, not who was to blame for it, and there is no minimum severity and no rarity percentage anywhere in section 32. That is why "medical misadventure" no longer returns anything useful when you search ACC's site: the category was retired more than twenty years ago.
What ACC declines, and why
Section 32 carries three exclusions and one clarification. Treatment injury does not include personal injury wholly or substantially caused by a person's underlying health condition, personal injury solely attributable to a resource allocation decision, or personal injury resulting from a person unreasonably withholding or delaying consent to treatment. And the fact that treatment did not achieve a desired result does not, of itself, constitute treatment injury (s32(2) and s32(3), retrieved 20 August 2026).
ACC's lodgement guide works those exclusions through with examples, and one of them is the clearest illustration of why identical outcomes get different answers. Two men of similar age both have a midline incision for emergency surgery, one for appendicitis and one for a ruptured abdominal aortic aneurysm. Both heal without infection and both develop a hernia at the incision site. The appendicitis patient, a never-smoker with no previous medical problems, is likely to be accepted. The aneurysm patient, a smoker with long standing high blood pressure, is likely to be declined, because in his case the hernia is an ordinary consequence (ACC lodgement guide, retrieved 20 August 2026). Same injury, same operation, different underlying health, different decision.
The single largest cause of declines is more basic than any of that. Lack of evidence of a physical injury caused by treatment accounts for almost two thirds of declined claims, and ACC states plainly that a claim lodged on symptoms alone, such as pain or aching, without an identifiable physical injury, will not be accepted (same guide, retrieved 20 August 2026).
What counts as an ordinary consequence has been litigated. ACC told providers in December 2018 that the point was "currently unsettled", that it was applying a test set by the High Court in November 2018 to all treatment injury claims then under investigation and to all claims subject to a current review or appeal, and that it was appealing the decision (ACC, 21 December 2018, retrieved 20 August 2026). ACC has not published an update to that page, so we do not repeat any account of how the appeal ended.
How many treatment injury claims does ACC accept?
Accepted treatment injury claims by treatment setting, by financial year of cover decision, from ACC, *Supporting Treatment Safety 2021*, Table 8 (July 2021, retrieved 20 August 2026).
| Financial year of decision | Public hospitals | Private hospitals (NZPSHA) | General practice | Other | Total |
|---|---|---|---|---|---|
| 2015/16 | 5,052 | 1,262 | 1,284 | 1,344 | 8,942 |
| 2016/17 | 5,737 | 1,352 | 1,421 | 1,450 | 9,960 |
| 2017/18 | 5,760 | 1,277 | 1,388 | 1,417 | 9,842 |
| 2018/19 | 6,231 | 1,466 | 1,428 | 1,381 | 10,506 |
| 2019/20 | 6,875 | 1,545 | 1,432 | 1,433 | 11,285 |
Accepted claims rose 26% across those five years. Public hospitals account for 1,823 of the 2,343 additional claims, or 78% of the whole increase, while general practice and other settings barely moved. Those two percentages are our arithmetic on ACC's published counts, not ACC's.
ACC is careful about what that growth means, and so are we. It notes that an increase in accepted claims does not necessarily mean more injuries are happening, since it could reflect clinicians becoming better informed about treatment injury and lodging more claims that meet the criteria (same report, retrieved 20 August 2026).
The bigger caveat is the date. Supporting Treatment Safety 2021 is the most recent treatment injury statistics report ACC has published, and it reports on 2019/20. There is no 2025 or 2026 edition. What ACC does publish for the current year is the money: the Treatment Injury Account paid $483 million in claims in the year to 30 June 2025, up from $427 million the year before (ACC Annual Report 2025, Treatment Injury Account statement of comprehensive revenue and expense, retrieved 20 August 2026).
What does ACC pay for a treatment injury?
The same things it pays for any accepted injury, and nothing extra for the fact that treatment caused it. There is no treatment injury payout schedule.
An accepted claim can bring treatment costs, rehabilitation, weekly compensation at up to 80% of pre-injury earnings capped at a gross maximum of $2,466.20 a week from 1 July 2026, and, for a permanent injury, lump sum compensation starting at $4,575.78 at 10% whole-person impairment (ACC, 11 June 2026, and ACC, financial support for a permanent injury, amounts valid 1 July 2026 to 30 June 2027, both retrieved 20 August 2026). We set the full impairment scale out in our guide to ACC lump sum payment amounts and the weekly figures in how much ACC pays.
How much money actually flows depends far more on which injury you have than on anything about the claim itself.
ACC payments made during 2019/20 divided by the number of claims active in 2019/20, for six injury types ACC reports separately. Claim counts and payment totals from ACC, *Supporting Treatment Safety 2021*, Table 1 (retrieved 20 August 2026). The division is our arithmetic. It is a snapshot of one year's spending per open claim, not the lifetime cost of a claim.
| Injury type | Accepted in 2019/20 | Active in 2019/20 | Payments in 2019/20 | Payments per active claim |
|---|---|---|---|---|
| Neonatal encephalopathy | 13 | 135 | $23,975,941 | $177,600 |
| Perioperative harm, excluding infection | 1,044 | 2,464 | $44,882,880 | $18,216 |
| Surgical mesh harm | 182 | 466 | $6,962,414 | $14,941 |
| Medication safety | 1,152 | 1,769 | $19,027,147 | $10,756 |
| Healthcare associated infections | 3,098 | 4,756 | $25,783,347 | $5,421 |
| Pressure injuries | 578 | 647 | $1,271,657 | $1,966 |
Healthcare associated infections are the most common treatment injury by a wide margin and among the cheapest per claim. Neonatal encephalopathy produced 13 accepted claims in that year and cost around 90 times as much per active claim as a pressure injury. If you are trying to work out what a treatment injury claim is "worth", the honest answer is that the distribution is extremely skewed and the average tells you almost nothing about your own file.
One thing an accepted claim also does is remove your alternatives. No person may bring proceedings in a New Zealand court for damages arising directly or indirectly out of personal injury covered by the Act, and no court or tribunal may award compensation for such an injury even in proceedings that are otherwise allowed (s317, retrieved 20 August 2026). Two routes survive: proceedings under sections 50 or 51 of the Health and Disability Commissioner Act 1994, which section 317(4) expressly preserves, and exemplary damages, which are dealt with separately at section 319 (retrieved 20 August 2026). ACC's entitlements are the compensation. There is no second bite for pain and suffering.
How long ACC has to decide, and the deadline that helps you
A treatment injury claim is a complicated claim in the language of the Act. ACC must investigate at its own expense and, no later than two months after lodgement, either decide the claim or tell you it needs an extension of no more than two further months. Further extensions can be agreed, but the decision must be made within nine months of lodgement (s57, retrieved 20 August 2026). ACC states the same thing in plain words to patients: it will tell you within two months if it cannot make a decision yet (ACC, last published 18 March 2025, retrieved 20 August 2026).
If ACC misses the applicable limit, the consequence is that you are regarded as having a decision that you have cover (s58, retrieved 20 August 2026). Across all complicated claims ACC's published average cover decision takes 39 days, and complicated claims were 2.5% of all new claims in 2025 (ACC, injury claim statistics, retrieved 20 August 2026).
The lodgement clock is more generous than for other claims, and this is the part most people get wrong. A treatment injury claim for cover must be lodged within 12 months after the later of the date the injury was first considered by a registered health professional to be a treatment injury, or the date you suffered the treatment injury (s53(4), retrieved 20 August 2026). And the date you suffered it is the date you first sought or received treatment for the symptoms, even if nobody knew at the time that earlier treatment was the cause (s38, retrieved 20 August 2026). ACC puts the practical version this way: if the injury shows up months or even years after the treatment, a claim can be made then.
There is also a general protection. ACC must not decline a claim lodged after the time limit on the ground that it was lodged late, unless the lateness prejudices ACC's ability to make decisions (s53(2), retrieved 20 August 2026). If your claim is declined, the review path and the three-month deadline that runs against you are set out in our guide to what happens when an ACC claim is declined.
What ACC does with your claim besides deciding it
A treatment injury claim is also a safety report. If ACC believes, from information gathered while processing a claim, that there is a risk of harm to the public, it must report that risk (s284, retrieved 20 August 2026). ACC says all claims are assessed for risk of harm, and that claims involving a failure to provide treatment with significant worsening of a person's health are more likely to be reported to a registration body or other relevant authority (ACC lodgement guide, retrieved 20 August 2026).
That is separate from a complaint. Health professionals are obliged to tell you about your right to consider a complaint to the Health and Disability Commissioner where you have been harmed by treatment, and lodging with ACC does not make that complaint for you (same guide). The claim itself must be lodged with your consent, because it hands your health information to ACC, and it has to be lodged by a registered health professional rather than by you. Cover extends to injuries caused by treatment for an injury ACC already covers (ACC, injuries we cover, last published 1 September 2025, retrieved 20 August 2026).
What is not published
Three gaps are worth naming rather than filling with estimates.
ACC has not published a treatment injury statistics report since Supporting Treatment Safety 2021, which covers 2019/20. Every claim count on this page is therefore five years old. We have not scaled those counts forward, because the growth rate in accepted claims and the growth rate in Treatment Injury Account spending are different things and one cannot be derived from the other.
ACC does not publish a current decline rate for treatment injury claims specifically. The "on average a third" figure comes from ACC's own lodgement guide, which carries the reference ACC7972 and a March 2019 date, and refers to district health boards, which no longer exist. It is ACC's most recent published statement on the point that we can find.
ACC does not publish average or typical payment amounts for a treatment injury claim, and neither do we. The per-claim figures charted above are one year of spending divided by claims open in that year, which is not what a claim costs over its life.
Where this leaves you
Treatment injury cover is broader than the test it replaced, but it is still cover for physical harm caused by treatment rather than compensation for a bad outcome, and it comes with a bar on suing for anything more. It pays the same 80% of earnings, subject to the same cap, as any other ACC claim, which is where the household budget usually breaks. That gap, and the illnesses ACC does not touch at all, is set out in what ACC does not cover.
To size what a long time off work would cost you, start with our income protection calculator. QuoteHub is operated by Craig Smith Business Services Limited, trading as Smiths Insurance and KiwiSaver, a licensed Financial Advice Provider (FSP712931). Our panel is listed on our disclosure page.
References
- Accident Compensation Act 2001, s32 Treatment injury (retrieved 20 August 2026): the three-part test, the three exclusions, the clinical trial provisions and the infection extension
- Accident Compensation Act 2001, s33 Treatment (retrieved 20 August 2026): the eight limbs of the definition of treatment
- Accident Compensation Act 2001, s34 Cover for personal injury caused by medical misadventure before 1 July 2005 (retrieved 20 August 2026)
- Accident Compensation Act 2001, s38, s53, s57, s58 (retrieved 20 August 2026): date of injury, lodgement time limits, complicated claim timeframes and deemed cover
- Accident Compensation Act 2001, s284 Reporting of risk of harm to public and s317 Proceedings for personal injury (retrieved 20 August 2026)
- Accident Insurance Act 1998, ss35 to 37 (retrieved 20 August 2026): the medical misadventure, medical error and medical mishap definitions, including the 14-day, 28-day and 1% thresholds
- ACC, Treatment Injury Claim Lodgement Guide (ACC7972, March 2019, retrieved 20 August 2026): the one-third decline rate, the two-thirds no-physical-injury finding, the worked examples and the nine-month timeframe
- ACC, Supporting Treatment Safety 2021 (July 2021, retrieved 20 August 2026): 2019/20 decision and acceptance counts, Table 1 injury type claims and payments, Table 8 claims by setting
- ACC, Annual Report 2025 (retrieved 20 August 2026): Treatment Injury Account claims paid, 2024 and 2025
- ACC, injury claim statistics (retrieved 20 August 2026): complicated claim share and average cover decision time
- ACC, Treatment we can help pay for (last published 18 March 2025) and Injuries we cover (last published 1 September 2025), both retrieved 20 August 2026
- ACC, 'Ordinary consequence' as a factor in treatment injuries (21 December 2018, retrieved 20 August 2026)
- ACC, Changes to ACC client payments from 1 July 2026 (11 June 2026) and Financial support for a permanent injury, both retrieved 20 August 2026
Disclaimer: This article is general information only and does not constitute personalised financial advice, legal advice or medical advice. Every figure on this page is reproduced from ACC or from New Zealand legislation as at the date stated beside it, and ACC's most recent published treatment injury statistics report covers the 2019/20 year. Whether any particular injury is covered is a decision for ACC on the facts of that claim. QuoteHub is operated by Craig Smith Business Services Limited, trading as Smiths Insurance and KiwiSaver, a licensed Financial Advice Provider (FSP712931), Christchurch.
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