The government can reduce dependence on oil revenues and meet current expenditures by broadening and defining new TAX bases. CAPITAL GAINS TAX has been introduced in different countries today; this TAX is a type of income and property TAX. Its important economic effects are to improve income distribution and meetinggovernment spending. It is important to note that in developing TAX legislation, the common TAX system should be consistent with the Islamic TAX system and religious foundations. The present paper reviews other countries' experiences on CAPITAL GAINS TAX and presents Islamic jurisprudence (feqh- e - Islami) view on this TAX and focuses on its related regulations with the aim to reform TAX structure due to its consistency with religious foundations. The results indicate that from the viewpoint of Ahlolbait school, one fifth (khoms) of CAPITAL GAINS has great similarities and some differences with CAPITAL GAINS TAX.

CAPITAL GAINS TAX is capable to regulate the behavior of economic agents in the housing market. This kind of TAX could drive some speculative uses out of the housing market. This study aims to determine the capacity of CAPITAL GAINS TAX on residential units in Isfahan City. For this purpose, a TAXation model is promoted, then, a calculation model for estimating CAPITAL GAINS TAX capacity on residential units in Isfahan City has been designed. In this model, there have been used several variables such as sales prices, the number of residential units, the maintenance period of the residential unit, the average annual growth of the housing price, the TAX rate on CAPITAL GAINS, and the probability density function and its cumulative one of the maintenance period. The model was calculated by using R software and doing 32 lines of code. The lowest TAX capacity estimation is about 350 billion Tomans and the highest one is about 1000 billion Tomans. The results show that firstly, the number of transactions has a direct effect on the CAPITAL gain TAX capacity. Secondly, the revenue from CAPITAL GAINS TAX in the short run is much larger than in the medium period. In other words, in the short term, because economic factors don’t still adjust, CAPITAL GAINS TAX yields more revenue, but in the long term by adjusting the behavior of house owners, TAX revenues vanished. This effect in public finance literature is called the lock-in effect.