The Morrison government's push to simplify the way welfare recipients report income may lead to another robo-debt "disaster", social security advocates say.
They've used a parliamentary inquiry on Monday to call on the federal government to delay changes so the new system can be tested.
But the government agency responsible says its preference is to begin the new reporting system at the start of the coming financial year.
In January, the federal government proposed updating welfare laws so recipients report actual income and not an estimate based on hours worked and income.
It would also use payroll data from the Australian Taxation Office to pre-fill income reports.
The National Social Security Rights Network says inaccurate information provided by the recipient would supersede more accurate tax office data.
Solicitor Daniel Turner said this was a recipe for overpayments and the recipient owing the government money.
He said it was important the lessons from the so-called robo-debt disaster were learned.
"People have lost a great deal of trust in the system because of robo-debt," Mr Turner said.
"It's been catastrophic in terms of the trust that people have in the social security system and that's a tragic result."
The network wants the onus to be on the government to confirm a recipient's income, seeing as it had better access to more accurate income data.
Australian Council of Social Service senior advisor Charmaine Crowe warned tax office data could also be inaccurate, but recipients may assume it was correct.
"I think there's a risk that people will assume that the government has gotten it right," Ms Crowe said.
She said it would be worth asking the tax office what its experience had been with pre-filled tax returns.
Both groups called on the government to delay changes so welfare advocates could troubleshoot the system.
"There's no need to rush this bill," Ms Crowe said.
"To compare what happened with robo-debt, there was no consultation with experts at all."
The Department of Social Services, which administers the welfare system, said it's aiming to start the new scheme from July 1, pending legislation.
"The sooner we can change it from earned (income) to received, we see that as a positive," acting deputy secretary Shane Bennett said.
When proposing the changes in January, the government hoped the new system would prevent recipients being owed money or paid too much, and save $2.1 billion in welfare overpayments.
The government's welfare debt recovery program, commonly referred to as robo-debt, was recently declared unlawful by a federal court.
The government has wound back the scheme, which is also facing a class action lawsuit.
Australian Associated Press