AbstractOne of the new business activities which has emerged in recent years is the creation and development of e-commerce. With the spread of e-commerce, there is the possibility of tax evasion in new revenues that were traditionally collected before. On the other hand, tax capacity is the economic capacity of a country to withstand the pressure of various taxes. In other words, it is the amount that people can pay in taxes. Determining tax capacity is a difficult and important task. In this regard, a precise estimate of tax capacity and finding its available resources seem necessary. Therefore, given the importance of this issue, the present study first tries to investigate the tax capacity, tax collection from e-commerce sector, and then it intends to estimate the tax capacity of the e-commerce sector as a regime in Iran. In this study, the tax capacity of e-commerce in Iran during the period ۱۹۷۳-۲۰۱۳ has been estimated. The results of this study showed that the total tax capacity follows a three-regime behavior. In all three regimes, the independent variables had a significant effect on the total tax capacity, but the size of these coefficients was different in each of the regimes and even in some cases it was different for the effect. Based on the results, it can be stated that the degree of impact and the direction of the impact of the fundamental variables of total tax capacity on tax capacity varies depending on economic conditions.