Another Work and Income related privacy breach has come to light, following three already revealed this week.
In the latest incident, documents that went missing after Wellington man Graham Wills handed them in at a Work and Income office later turned up in his letterbox, apparently returned by a stranger.
Mr Wills' sickness benefit was stopped last year after he was told he no longer met requirements because he hadn't provided an updated medical certificate.
He had already delivered a medical certificate and updated forms to his local Winz office and received a date-stamped receipt for the documents, but was told he had to do it again.
He complied and sent them in again.
Several days later he received an envelope with the original medical certificate and other missing documents in it.
"It had a wee note from someone simply signing themselves as 'J' - saying that these were amongst documents that had been sent to them," Mr Wills said.
"Whoever it was, it was very nice of them to drive by and pop them in my mail box."
He didn't raise it as a privacy breach at the time, saying he was unwell at the time and didn't want the added stress of a "battle" with Winz.
"Work and Income really made my life a misery last year. I am now retired and I don't have Work and Income on my back any more.
Head of Winz Debbie Power said the incident was not brought to the attention of staff when they had spoken to Mr Wills previously.
"If our staff make a mistake we own it and do what we can to fix it. In order to do this, however, we need people to let us know what's happened so we can look into it."
A spokeswoman for Social Development Minister Paula Bennett said the minister would not comment on every single operational issue that came up.
"The department needs to answer to these kinds of things. It's not that this is just happening in the last week, it's been happening for years - these sorts of instances happen in an organisation like that that has such heavy volumes of traffic," the spokeswoman said.
"The Privacy Commissioner has investigated loads of different cases like this and very often they have said it's not systemic and they're satisfied it's human error."
Earlier this week it was revealed a Masterton woman received a confidential document containing another client's details on a piece of scrap paper.
In a second case a Wanganui man said he went to Winz for a work seminar and was given a folder with job listings. He said it contained a document with another client's personal information.
In a third incident, Whitirea student Jean Eltringham was given another client's details in a pile of papers during a meeting at a Kapiti Winz office in August.
Ms Bennett said in Parliament this week there was no systemic issues with privacy at the Ministry of Social Development and has declined to extend an existing inquiry on the Ministry of Social Development's information technology systems to look at the latest privacy breaches.