CHICAGO (WBBM) – State officials say they have collected millions of dollars in unpaid taxes from gas station operators since they began an aggressive enforcement effort.

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Last year, the Department of Revenue and the Attorney General’s office began a voluntary compliance program, increased audits and intensified collection of unpaid taxes from gasoline station owners, generating about $12.5 million over a 10-month period.

Recently, the effort was stepped up with the filing of criminal charges against five gas station operators. Since then, an additional $9.3 million has been collected for a total of approximately $22 million.

Gasoline sales are reported on a monthly basis. Officials determined that a fraudulent practice had developed of evading the payment of the taxes by falsely reporting gasoline sales figures.