ACC has been ordered to pay lost wages and compensation to a worker who was sacked over a privacy breach.
But the Employment Relations Authority found the employee, Keshni Mala, should not be reinstated and was also partly at fault.
Ms Mala claimed she was unjustifiably suspended and dismissed after disclosing confidential client information by email.
In August 2012 Ms Mala, a case co-ordinator in ACC's Wellington short term claims centre, sent an email to a client in Hawkes Bay, identified as "J'', containing private information about other clients.
The email contained a screen shot of her computer with windows open showing information about other clients.
The authority determination said J rang Ms Mala and told her the email did not appear to be for him. Ms Mala then sent the same email a second time.
Ms Mala did not report the breach to ACC, or file the emails in the document management system. She made a file note about the phone call with J, but not its content.
She later said she wasn't aware of the privacy breach until alerted by ACC, which was made aware when a person acting on behalf of J made a complaint to the ACC Minister.
During the investigation, ACC became aware of another incident when Ms Mala accidentally sent information to the wrong email address.
She was suspended on full pay during the investigation.
In a meeting with managers, Ms Mala said she had phoned J to advise of an incorrect date in the first email, and advised him to delete it before sending another with an enlarged font.
At a subsequent meeting she said she couldn't remember the events in enough detail to provide further comment.
ACC made a final decision on November 29 that Ms Mala's version of events was not plausible, her actions amounted to serious misconduct and she was summarily dismissed.
The authority found ACC's process was flawed because a manager who had delegated responsibility for the matter should not have sub-delegated this to the manager who was also conducting the inquiry.
However, this was unlikely to have affected the outcome.
It also found the standard of proof had not been met in relation to claims Ms Mala was dishonest about her actions.
The authority found Ms Mala did have a personal grievance, but had significantly contributed through her own fault. There were issues of care and responsibility, and having disclosed private information twice it was not practical or reasonable for ACC to reinstate her.
She was awarded three months' wages, less 25 per cent for her own contribution, and $6000 compensation for hurt and humiliation, reduced from $8000 for her "blameworthy conduct.''
Spokeswoman Stephanie Melville said privacy was ACC's number one priority.
"While we acknowledge the ERA decision we do not resile from the actions we took to protect client privacy.''