The objective of this study was to evaluate the internal control system in operation at power holding company of Nigeria Plc in Enugu State with a view to knowing its impact on revenue generation in the state. A sample of 40 was selected for the study randomly. The questionnaires were used in gathering the primary data while secondary data were collected from the work of others in the form of literature review. The data collected were analyzed using the chi-square (x2) as the statistical tool to determine the valuation of the hypothesis. The findings concluded that weak internal control system encourages collusion fraud loss of revenue, embezzlement and computation. This have always impeded the company’s ability to effectively supply electricity to customers and there from generate revenue. Internal audit system ensures operations compliance with set policies, promoting accuracy and reliability of transactions recording. In addition, effective internal control system ensure effective recommends the remodeling of the company’s internal control system and strengthening of the investigating unit. The components sectors of the present corporate Power Holding Company of Nigeria PLC should be unbundled into separate distinct independent entities that handle generation, transmission, distribution and marketing. It further recommends that prepaid meters should be seen as an alternative to further accumulate debts.