ACC healthcare harm claims rejected at 26 times rate of standard claims
Tuesday, 2 June 2026
More than one in four ACC claims for healthcare-related harm are declined ‒ 26 times the rejection rate for standard claims.
Of the 64,314 Kiwis who made claims in the past three years for medical mishaps or other treatment injuries, 16,614 were turned down, according to new figures provided to The Post.
From 2023-2025, more than a quarter of treatment injury claims (26%) were rejected, compared with just 1% of “non-complicated” claims. That decline rate spiked to 29% for claims lodged last year.
The growing rejection rate comes as healthcare harm claims soar and ACC tries to rein in ballooning costs.
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The Post last year revealed treatment injury claims for infections, pressure injuries, surgery-related injuries, drug errors, surgical mesh and neonatal brain injuries have almost doubled in a decade, with costs trebling.
Experts say the high decline rate shows how difficult treatment injury cases are to prove. And one lawyer is calling for a free, independent expert evidence service to help patients challenge decisions to deny them help.
Treatment injury replaced ACC’s medical misadventure category in 2005. Accepted claims can access compensation, treatment and rehabilitation, depending on the situation.
Claims can be expensive and long-term, such as oxygen deprivation at birth causing life-long disability.
But lawyers say the category’s legal test is notoriously tough. As well as proving that the treatment (or lack of it) caused the injury, claimants also have to show the injury is not “an ordinary consequence” of the treatment.
John Miller, an expert in ACC claims, previously told The Post his firm had “stacks” of cases of declined treatment injury claims, while ACC specialist Hazel Armstrong said it was 'an extremely difficult area of law”.
Lawyer and researcher Warren Forster said rejecting more than one in four claims was a lot, given patients needed a specialist medical referral to even make a claim.
“It’s a very high decline rate, bearing in mind this is meant to be a no-fault system, and you don’t even get to the start line, until you get a medical certificate that someone’s experienced treatment injury.”
The increasing decline rate mattered, because it was so difficult to overturn a rejection, Forster said.
“It’s a really, really hard test to overcome, and to expect people to be able to challenge that themselves is impossible. Imagine you had a specialist type of cancer and there was no GP there to help you get that treatment. You had to go and find someone to give you that treatment, and then find a way to fund that treatment.
“That’s basically what’s happening with these treatment injury cases. You need a particular type of expert, and good luck finding them.”
A funded service to give claimants access to independent experts would make the system fairer, Forster said.
Harm from a lack of treatment - such as a missed diagnosis or misdiagnosis - was also hard to prove, Forster said.
“I’ve had a series of cases around failure to diagnose endometriosis, and ACC basically says, well, we don’t know if it would have made any difference if we’d treated it.”
Endometriosis New Zealand chief executive Tanya Cooke was aware of recent cases of women taking treatment injury claims for misdiagnosis.
The best hope to avoid more claims, was to help doctors recognise the complex condition by adopting new clinical guidelines already in place in Australia, she said.
“That complexity does not lessen the frustration and harm caused when diagnosis is delayed or a condition is misdiagnosed, and we know many people with endometriosis have spent years trying to have their symptoms recognised.”
ACC said there could be many reasons for declining a treatment injury claim, including lack of any physical injury caused by the treatment, a lack of a causal link, an underlying condition, or the injury being an “ordinary consequence” of treatment.
The number of treatment injury claims lodged with ACC should not be taken as an accurate gauge of how often patients are harmed by healthcare, or the quality of care, it added.