The purpose of this paper is to design a unique pricing system (price-cap) for Iran's water and wastewater industry to ensure fair pricing for its customers, encourage effective investment planning, and improve corporate productivity and efficiency. To this end, the translog frontier cost function form using the panel- data of thirty-five (35) water and wastewater companies over the period 2012-2017 is used to calculate the aforementioned components and X-factor and use it in the price-cap model for a five-year period, has been used. The price ceiling decreasing for the most efficient company was 2% and for the most inefficient company was 28%. In other words, in the first year of implementation of the price ceiling adjustment model, the most efficient water and wastewater company will be allowed to decrease its base or initial price by 2%, but the most inefficient company will be allowed to more decrease by 28%. It is this incentive that fulfills the purpose of implementing the price-cap model as an incentive regulation method
