Seven employees from Revenue Quebec, IBM and Informatique EBR were arrested last week in connection with the same investigation.
The government employees stand accused of providing privileged information about an upcoming $24-million contract to a consortium made up of IBM and Quebec company Informatique EBR Inc.
UPAC officials allege the companies then used that information to design their bid before the public call for tenders was launched.
The contract in question involved supplying the technology for a Revenue Quebec data management system.
UPAC confirmed Monday that Daniel Letourneau, the final suspect sought in the investigation, had been arrested.
Letourneau, who works for IBM, faces charges of fraud, embezzlement and conspiracy to commit fraud.
He is scheduled to appear in court on June 10.