Top-ranking Services Australia bureaucrats were grilled about security measures for paper and digital proof of immunisation at a parliamentary hearing on Thursday.

Independent senator Rex Patrick was incredulous after officials confirmed no work was being done to change paper vaccination certificates.

"Surely you can't suggest that in circumstances where there are easily available technologies to at least make it far more difficult to forge that you're not doing anything about it," he told the inquiry.

"I find that extraordinary. The government is doing nothing about forgeries and that actually devalues the certificate itself."

Services Australia chief executive Rebecca Skinner said the same paper system with government watermarks used for other immunisation records would be used for coronavirus.

Ms Skinner said documents used to gain access to child care and government benefits had been a part of service delivery for years.

"We are not changing our approach to providing the paper-based service we have provided for a number of years," she told senators.

Senator Patrick said he had been able to forge a paper vaccination certificate in 10 minutes.

"I could be wandering around utilising that now and if you don't think that's a problem then that's a problem in itself," he said.

Ms Skinner said it was up to people to raise issues about forgeries with the federal government.

"If there is a concern about that, we think people should come to us. That's how we've treated both the hard copy and the digital copy," she said.

She said the rules around using the coat of arms and government watermarks made faking documents harder.

"We want to just allow people to get the documents they are used to getting. Where there is some permission related to it, that's been a matter for the states," Ms Skinner said.

"I have no systematic evidence of there being rackets of people selling or producing Australian documentation.

"There is no business case to do so. We are approaching vaccination rates in the very high percentages."

But Senator Patrick argued coronavirus certificates used to access venues needed stronger forgery proofing than documents used for government payments.

"Having a vaccination certificate that is easily forged undermines the health measures."

Services Australia also answered questions about digital vaccination certificates to be used for international travel.

Ms Skinner stressed the documents were not vaccine passports, which they have widely been characterised as.

"The plan is to have all of the technology in place so it is settled and tested before the policy decisions are in place," she said.

"We are confident the technology will all be in place within the next sort of two to three weeks - well before the end of October."

Australian Associated Press