Witnesses began giving evidence to the Queensland Health Payroll System Commission of Inquiry in Brisbane as it resumed on Monday.
Thousands of public servants were underpaid, overpaid, or unpaid after a flawed IBM computer system was introduced in March 2010 by the former government.
More than 50,000 staff members are believed to have been overpaid more than AU$90 million.
Counsel assisting the inquiry, Peter Flanagan SC, said in his opening address that there seemed to be an "atmosphere of urgency" during the initial tendering process, possibly because of a push to upgrade from the outdated Lattice system.
"We will inquire whether, and to what extent, it was justified to adopt such an approach to cut corners ... and whether that was warranted in such a large and important project," Flanagan told the inquiry.
The first two-week sitting will see 23 witnesses take the stand.
They will give evidence about the procurement and implementation process to determine whether any laws, contracts, or codes of conduct were broken, and why costs blew out.
The inquiry will also look into allegations of collusion surrounding the process.
The claims were first raised by a whistleblower during an ABC Radio interview in November last year, Flanagan said.
He said that IT company Accenture had received higher scores than IBM, which eventually won the contract, during initial tender assessments.
Former Accenture partner Marcus Salouk, the first person to give evidence on Monday, was sceptical of the government's initial AU$300 million budget for the payroll system rollout.
He said CorpTech, the government's IT arm, had already spent AU$200 million before tenders went out, and it wouldn't have been possible to complete the job within the remaining budget.
"We wanted to make it clear that there were no silver bullets," Salouk said. "There was no easy way to fix this thing.
"Treasury had done the project inefficiently for a number of years, and there was a cost associated with that."
About 35 volumes of documents have been tendered in the inquiry, which is expected to cost about AU$5 million.
It continues before Commissioner Richard Chesterman.