ANASTASIA MCCARDEL: Bruce had the biggest heart of all people. Just the most easy-going, decent person you could ever meet.

PAUL FARRELL, REPORTER: Bruce McCardel was adored by his family and friends and was a doting uncle.

ANASTASIA MCCARDEL: Torquay Bowls was pretty important to him because it was the only sport he could probably enjoy himself.

PAUL FARRELL: Bruce suffered from a long term cardiac condition.

ANASTASIA MCCARDEL: Bruce had it all his life and then he lived until he was 49.

PAUL FARRELL: Although he worked part-time, Bruce was receiving a disability pension when he died last November.

ANASTASIA MCCARDEL: His heart just stopped. He died about 3.30 in the morning and I was there with another friend of Bruce's, just holding his hand.

PAUL FARRELL: Six months after Bruce died, his mother received an unexpected phone call.

ANASTASIA MCCARDEL: She asked me if I was Anastasia McCardel and I said "Yes".

And she said "I would like to give you my condolences for the death of your son" and I said "Thank you but who are you?"

And that was when she said she was from the Department of Human Services.

And I said "Yes, well, what do you want?"

And she said "Well, I'm ringing about Bruce and his Centrelink payments".

PAUL FARRELL: Anastasia couldn't comprehend why Centrelink had contacted her.

ANASTASIA MCCARDEL: It was basically along the lines of Bruce owed the money and she made out that I was responsible for those payments.

PAUL FARRELL: She later received a letter from Centrelink, enclosed was a debt notice addressed to Bruce.

It said he owed Centrelink more than $6,500. The letter thanked Bruce for checking his past income information.

ANASTASIA MCCARDEL: I also wanted to know how they thought Bruce would have worked his way through his paperwork when he actually was dead.

PAUL FARRELL: Do you think Bruce could have owed any money?

ANASTASIA MCCARDEL: Bruce always was very careful with what he did with his Centrelink.

PAUL FARRELL: Do you think there is something wrong with the system that mails debt letters out to people who have died?

ANASTASIA MCCARDEL: Yeah definitely. No, they have certainly not done the right thing here.

KATHERINE BOYLE, WELFARE RIGHTS CENTRE: We are talking about a computer system, that is why they are called robo-debts.

It is a computer program which data matches with the Australian Tax Office. It is a computer program which sends out the letters.

PAUL FARRELL: 7.30 has been inundated with stories from people who have received unexpected debts from Centrelink.

We spoke to a woman who had received Newstart who had a $4,500 debt wiped.

A young woman with an intellectual disability who had an almost $3,000 debt waived when she challenged it and an aged pensioner fighting a $6,000 Centrelink debt.

GAVIN SILBERT QC, FORMER CROWN PROSECUTOR: The so-called debts, and I don't concede they are legally enforceable debts but whatever they are, they arise as a result of the total incompetence of Centrelink.

TELEPHONE OPERATOR: So what is the issue that you're having with Centrelink?

PAUL FARRELL: Sydney's Welfare Rights Centre has also been swamped with calls from people desperate for answers about robo-debts.

TELEPHONE OPERATOR: Is that something that Centrelink asked for evidence of?

KATHERINE BOYLE: She had no idea why she had a $14,000 debt.

We are seeing more robo-debts come through every week. It's a nightmare of a system for most people to try and navigate.

They are being encouraged to agree to what are potentially wildly inaccurate debts if the debts exist at all.

PAUL FARRELL: Tim Cahalan has received government support payments since he was a child.

He moved onto a full disability pension when he turned 18.

He's a member of the ALP and works four days a week for a state government agency in Adelaide.

TIM CAHALAN: I go to my local Centrelink office with my pay slips and just give them to one of the workers behind a desk so they could process it to a computer.

PENNY CAHALAN: He has got epilepsy and an intellectual disability and medical issues as well but really, he has been quite remarkable in the way he's handled all of that.

PAUL FARRELL: Last month, Tim received a $3,000 debt notice from Centrelink.

TIM CAHALAN: When I did get a letter and I assumed it was an invoice and I put it aside, but then they sent a reminder out to my mum who then told me about it.

PENNY CAHALAN: Do you have any idea how that happened?

TIM CAHALAN: No.

PENNY CAHALAN: I thought it was a mistake and I thought just going down to Centrelink and talking to them would clear it up and it would go away.

PAUL FARRELL: Tim went to his local branch to try to get some answers.

TIM CAHALAN: They didn't really give a reason. I think when I went in the first time they just referred me to a compliance people on the phone.

PENNY CAHALAN: It's not good enough simply to keep telling Tim and myself that it exists. I want to know where the debt was, what actually happened?

What months did he underreport his income or what months was he overpaid? Not just to be told it exists.

I don't really think that is a fair or equitable way to deal with anyone at any level.

You can't just tell people they owe thousands of dollars without providing any actual proof.

PAUL FARRELL: Leaked documents obtained by 7.30 reveal the pressure staff are under to finalise debts.

Centrelink staff have been given a performance guide for raising debts that measures tasks down to the minute.

Closing robodebt cases is a critical performance measure.

PENNY CAHALAN: What they seem to be doing is a cash grab, they are targeting a very vulnerable group who often don't have the ability to stand up to this kind of bullying.

This is just bullying very vulnerable people.

PAUL FARRELL: In a statement, the Department of Human Services told 7.30 that it balances the specific sensitivities of working with people who have an existing vulnerability and its obligations to ensure that people have been paid the right amount.

It said is regularly looks closely at sensitive cases to see what could have been done better.

ANASTASIA MCCARDEL: I just thought here is an opportunity to be able to actually do something about the Human Services Department and the way they are treating people without any thought whatsoever for the people they're dealing with.