An Australian serial robber claimed he was allowed into New Zealand four times before immigration authorities picked him up.
The 37-year-old - who was facing deportation - won an appeal to stay after arguing Immigration New Zealand had not noticed he had repeatedly disclosed his previous convictions.
The Immigration and Protection Tribunal upheld the unnamed Australian man's appeal against deportation.
He argued he had built a life, including being in a relationship and having a four-year-old son, after being allowed into the country, despite his police record.
The tribunal heard he was jailed for six-and-a-half years in total for six robberies and an assault in 2003 and 2004.
"He has always declared his criminal convictions on arrival in New Zealand but, as the arrival cards are destroyed every six months, the appellant is unable to establish the truth of his actions," the tribunal said in its summary.
"[He] has lived in New Zealand since 2012. Immigration New Zealand's error has resulted in the appellant having established a very positive life for himself here and asking him to leave now would be unduly harsh, particularly as he has not been in trouble with the law and instead has made significant contributions from both a family and employment standpoint."
He argued his relationship with a New Zealand woman, and the best interests of their son, amounted to humanitarian circumstances which should allow him to stay.
The tribunal agreed and noted: "As [he] has otherwise been truthful about his circumstances the tribunal extends him the benefit of the doubt with respect to his claim to have disclosed his criminal history on his arrival card on each occasion he arrived in New Zealand, as on his arrival card in May 2018."
Immigration New Zealand said travellers coming from visa waiver countries, including Australia, were asked questions about convictions on their arrival card and would be refused entry if they did not meet character requirements.
If not, Australians were granted a residence visa on arrival.
Five Australians were deported last year.
Last year, the then New Zealand high commissioner in Canberra told the Joint Standing Committee on Migration that Australia was deporting about one New Zealander a day.