Robodebt was an unlawful government program that saw thousands of welfare recipients pursued for debts that, in many cases, they did not owe. It was linked to a number of suicides.
Former prime minister Scott Morrison was referred for further investigation by the National Anti-Corruption Commission, for knowingly allowing cabinet to be misled over the scheme.
Senior public servants Kathryn Campbell, Catherine Halbert, Annette Musolino, Serena Wilson and Mark Withnell were also referred to the corruption watchdog.
On Wednesday, Mr Withnell and Ms Wilson were found to have engaged in serious corrupt conduct, but the others were cleared.
Federal police, the Australian Public Service Commission and heads of departments were also tasked with investigating further allegations of wrongdoing.
All investigations stemming from the royal commission had now been finalised, Attorney-General Michelle Rowland told parliament on Thursday.
"It was important to allow for each of these processes and investigations to run their course," she said.
The lack of consequences for those involved in the scheme is "grossly disappointing but not surprising", a victim of the program says.
Melbourne mother Felicity de Somerville had $11,500 drained by Centrelink from her bank account without warning under the scheme in 2017.
"I don't think any Australian should be surprised they're not going to take accountability for this and that no one's going to get in trouble, because that's the culture we're breeding," she said when asked by AAP what she made of the decision not to push for criminal charges.
The former nurse had just finished maternity leave when she found her account had been debited the equivalent of six months wages overnight despite having agreed to a payment plan.
It left her unable to afford medical care for her daughter, who was unwell at the time and caused immense distress for her and her husband, a welder then earning $45,000 a year.
"It really was horrible but I count myself lucky compared to what some others went through," Ms de Somerville said.
The watchdog found Mr Withnell, the ex-departmental general manager of business integrity, carried out corrupt conduct by intentionally misleading the Department of Social Services during the preparation of a cabinet submission in 2015.
It also found Ms Wilson, then department deputy secretary, carried out corrupt conduct by misleading the Commonwealth Ombudsman during an investigation in 2017.
But the watchdog said the findings would not be referred to the Commonwealth Department of Public Prosecutions to consider criminal charges.
"There was insufficient admissible evidence to establish the alleged offences against either Mr Withnell or Ms Wilson beyond reasonable doubt," the report said.
"Key admissions and statements made during this investigation are not admissible in criminal proceedings."
Mr Morrison was found not to be corrupt.
His failure to realise that bureaucratic advice was misleading was put down to shortcomings by federal departments.
Between 2016 and 2019, the former coalition government's robodebt scheme recovered more than $750 million from almost 400,000 people.
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