After critics of the program blamed its problems on staff cuts removing people from the debt raising process, the DHS told a Senate inquiry on Tuesday that clients needed to provide the right data to avoid inaccurate debt notices.

Department general manager of integrity modernisation Jason McNamara said the recent Commonwealth Ombudsman report on the online compliance intervention program found it was "providing accurate debt outcomes".

"I don't accept that there's staff cuts in the area, very much the opposite in compliance," he said.

Mr McNamara said the system relied on people giving Centrelink the right information and that in most cases the agency found clients' original income reporting was incorrect.

"We are finding in the vast majority of cases that third party information is accurate and what people originally told us was not. Hence why we have so many debts raised through this measure."

Mr McNamara said DHS staff used to manually assess whether a client had a debt when they called after receiving a letter about a discrepancy with their reported income.

However staff were not involved in deciding which clients received an initial letter about the discrepancy under the manual system, he said.

Centrelink letters now directed clients to update their information online, where the agency's system would calculate whether they owed a debt, and direct any complex cases to call directly.

The department had no plans to restore staff to their former role manually assessing claims for clients, Mr McNamara said.

"If they give the wrong data to the compliance officer we also won't get the right outcome either."

Australian Association of Social Workers national president Karen Healy told Senators the removal of human oversight from the debt collection program had undermined public confidence in the system.

"It's a large government agency which appears faceless to them and there's no option to negotiate. That is the problem for many people," she said.

"The ability to advance their case individually against a perceived very large, powerful faceless bureaucracy is very different to owing a debt to someone who you have a personal relationship with.

"It can reinforce people's sense of powerlessness."

Changes to the department's data analysis would better detect the likelihood an income discrepancy would result in a debt for a client, Mr McNamara said.

"That's where we think we can improve and that will help recipients because we'll be sending less letters to people who don't have a debt."

Mr McNamara conceded Centrelink learnt from the backlash to its initial debt letters, criticised for aggressive language and misleading clients into believing they owed money.

"I think that's important because I think people need to understand that they're just interacting with us and they're providing some information," he said.

"Trying to tone it better was a lesson and that's something we've taken on board."

He also admitted the DHS needed to talk to stakeholders more before overhauling its welfare compliance system.

The department will expand its manual assessments of assets and investments for clients from July, however online assessment was still "evolving" and would not be implemented at the start of the financial year, the inquiry heard.