For a number of weeks the federal government agency Centrelink has been sending out automatically generated debt notices to current and former payment recipients.
Now, an online campaign has begun sharing accounts of people disputing the amounts they're said to owe the government.
Lyndsey Jackson helped create the 'Not My Debt' website and social media pages.
She says some of the most socio-economically vulnerable people are being incorrectly sent letters from Centrelink demanding repayment.
"These are not people that have defrauded the system. These are people that have legitimately followed the processes that are set up and that Centrelink was designed for, and they've done all the right things, and now, three, four, five years later they're being hit with these debts. And that's a dangerous precedent to be setting."
The automated system was introduced in July as part of an effort by the federal government to recover around $4 billion in estimated welfare overpayments.