پژوهشنامه مالیات
سال شانزدهم شماره 49 (تابستان 1387)

Tax effort shows the percentage of nominal tax revenues being realized. In other words, the difference between the nominal and the realized tax bases indicates the tax effort and if the nominal tax base equals the realized, then we can say that a full tax effort has occurred. Both the economic literature and the empirical studies have considered the tax to national income ratio as the tax effort. Variables determining tax effort are classified into two categories (Bird, 2002): First, supply-side variables which are being used in most traditional studies including such variables as per capita income, share of value added of the agriculture sector, inflation, openness of the economy, and the extent to which tax collection authorities make efforts. Second, demand-side variables which explain the roles of social institutions and emphasize on the citizen's inherent motives and people's attitudes towards making use of benefits of paying taxes. The most important demand-side variables are tax morality, shadow economy, tax evasion and income distribution inequalities. In this paper, two methods have been used to study tax effort. The first is the econometrics method which has been used in most domestic and foreign studies. In this method, a part of demand-side variables such as per capita income, share of value added of the agriculture sector, inflation, and population growth is taken into account and after estimating the model, the tax effort exerted is measured in respect to taxes on consumption, wealth, business income, and corporate income both in the whole country and in the seven provinces of Tehran, Guilan, East Azerbaijan, Khorassan, Isfahan, Khouzestan, and Fars. But as for the second method, namely, the "system dynamics approach", the preliminaries of designing a model have been mentioned and the advantages thereof have been described. This method resolves the shortcomings of econometrical models and is able to make use of most of supply-side and demand-side variables and as such, it can eventually be used in forecasting tax revenues.

In this paper, I deal with estimating Fars province taxable capacity through OLS regression model and making use of time series data of a period of 21 years. Among the most important variables affecting the province tax levels and taxable taxes in respect of total taxes, tax on business, and corporate tax during the years 1983-2003, I have mentioned such variables as values of incomes and exports, value added of industry sector, value of exports, and the province total revenues. The findings show that there are tax gaps in all three kinds of taxes mentioned above due to the existence of potential capacities in the sectors thereof. Tax effort index during the intended period has been less than unit but it has gradually improved in recent years. As the tax elasticity is lower than one, it can be concluded that the tax system has relatively been inefficient in the early years of the period under investigation though in recent years, the tax performance has relatively been raised.

One of the essential functions of governments in all economies is to satisfy the prerequisites of achieving economic equality and to fairly distribute the acquired incomes. Taxes are considered as one of policy-making instruments to be used for achieving these goals. An exploration of changes in the welfare conditions of people during certain periods of time would make it possible to analyze the outcomes of economic policies adopted throughout those periods. The present research has been devoted to an investigation of the impacts of taxes on the income distribution during the period 1974-2005. To do the task, I have firstly explained the factors affecting the inequalities and the conditions of income distribution during the intended period and then, through making use of econometrical techniques and OLS model, I have studied the impacts of taxes on the income distribution index (Gini coefficient). Research findings indicate that an increase in the Tax/GDP ratio as well as a decrease in the rates of direct taxes (in comparison with the rates of indirect taxes), results in the raising of the Gini coefficient.

Tax revenues are one the most important resources of the government incomes and, therefore, the issue of how to provide tax resources in order to achieve the required government income is of great significance. The Iranian tax system is not as efficient as it must be in spite of the fact that it has a long history as a governmental organization. So, doing reforms in the state fiscal structure is among the most important issues within the economic plans and policies. One of the fundamentals of the Islamic Republic of Iran's Third Economic, Social and Cultural Development Plan has been devoted to reforms in the state tax system which led to the establishment of the Iranian National Tax Administration (INTA) in the year 2001. Subsequently, by virtue of the article 272 of the Iranian Direct Taxes Act, making use of services provided by certified public accountants and by members of Iranian Association of Certified Public Accountants (IACPA) for tax audit purposes was again revived. On the other hand, due to changes in money values in different times on the basis of changes in the general levels of prices, tax lags will result in a decrease of real government revenues and as such, it seems necessary to discuss about how to collect taxes in due time. The present research aims at studying the impacts of tax audits by IACPA members on tax lags through making a comparison between tax performances of the corporations using IACPA services prior and after the implementation of the article 272. Research findings indicate that the implementation of the above-mentioned article has resulted in an increase of legal tax lags in the statistical population under study.

Exploring the differences between impacts of Islamic taxes / ordinary taxes on investment requires recognition of their properties and their differences. The paper shows, through mentioning kinds of Islamic government financial resources and the characteristics of each one, that firstly, the low rate of Islamic taxes, their stability, and their payments being considered as an act of worship, all and all prevent the problem of inefficiency; secondly, the impacts of Khoms on the investment differ from the impacts of Zakah; thirdly, some taxes such as tax on consumption or salary are not taken into account within the discussion of Islamic taxes; and fourthly, the impacts of governmental taxes within Islamic environment may theoretically be similar to those of ordinary taxes. The paper has eventually explored the impacts of Islamic taxes on the investment and has showed that they have supported investments in various ways.

One of the financial duties referred to as 'vajeb' in Islamic instructions, is called as 'Khom's which literally means 'a fifth of one's annual net income' to be paid for charity purposes. The verse 41 of Al-Anfal chapter of the Holy Quran has necessitated payment of Khoms and the cases it is to be consumed for. According to Shia Imams, Khoms is generally imposed on seven categories one of which is called as 'Arbah-e Makaseb Khom's which is particularly dynamic and due to its rate and the circumstances under which it is levied, it seems to have the nature of so-called ordinary taxes in spite of some differences. Having in mind the cases where Khoms is to be consumed, it is obvious that the distributional goals have been among the most important objectives of its imposition. Khoms may have the least contrast to the principle of efficiency due to its domain of inclusion covering all kinds of income and its rate stability. According to what was said, in this paper, I have firstly mentioned the circumstanced under which Khoms is levied and the cases where individuals are exempted from paying it, and secondly, I have specified the domain of these two topics. Then, on the basis of viewpoints of some jurisconsults who have classified Khoms as one of the Islamic government's incomes and from a taxation standpoint, I have mentioned different methods of estimating it in the country. After that, regarding the economic information available about Arbah-e Makaseb Khoms and the variables and the parameters thereof, I have introduced Pareto's Two-side Distribution Method in order to estimate amounts of this Islamic tax category among the society's different income classes and I have measured its potential amounts for the years under investigation on the basis of available statistics. In the end, I have compared Gini coefficient- as an index of distribution- prior and after paying Khoms.

Legal structure of Kharaj tax has some essential differences with that of Zakah because the imposition of Kharaj is among the Islamic government's authorities and is not based on the individual's religious obligations. There are two properties for Kharaj tax which provide the basis for comparing it with VAT on consumption: "the inclusiveness of the tax base" and ''the flexibility of the rate".