In each regulatory period, the parameters of the reward and penalty scheme (RPS) vary based on the investment made by electricity distribution companies (EDCs) and imposed costs. In this paper, a novel dynamic model for determining the RPS parameters for each EDC is presented. This new model has three stages: (i) determination of the RPS parameters for the first regulatory period, (ii) the RPS decision-making model, and (iii) determination of the RPS parameters for the subsequent regulatory period. The proposed model was implemented for Iranian EDCs. Results verified the effectiveness of the proposed model in enhancing distribution system reliability.