The report said that errors occurred in some 380,000 of the roughly 8 million transactions processed since the ITS was implemented.

The ITS replaced a mainframe application with Java-based software that runs on IBM's WebSphere middleware platform and DB2 database.

CGI and DOR engineers in recent weeks have been analyzing data and testing to make sure that all defects are addressed, Engan said.

The DOR has calculated that it still owes 33 counties $1.8 million, while it has overpaid $2.8 million to 25 counties and the two sports districts, according to a report by State Auditor Janice Mueller.

In an interview, Mueller urged caution, asking that counties wait before collecting the remaining overpayments until the testing is complete and the ITS system proves reliable.