Critique and analysis of the famous opinion on determination of Khumsi year and the period of deducting expense from profit

According to the Islamic  jurists' Idjma, Khums of profits of income must be calculated after deduction of customary expenses of the duty-bound and those family members  entitled to receive maintenance; hence the need to determine the beginning and end of a period to calculate expenses. The results of this research are as follows: first. Determination of Khumsi year has not been expressed in any parts of the narrations and the Ali ibn Mahzyar's narration which is resorted to has been issued by the Infallible under the exceptional circumstances of the particular time and recourse may not be had thereto in this regard.  The authority of narrated Idjma is also refused given the opposition of some Islamic jurists and the fact that its source is known and due to its contradiction with Imam Sadegh’s narration. In addition, the beginning of this expanded duty is not either the start of the business or lapse of one year from the start of the business or the rise of profit, but the only criteria for duty to pay Khums is the rise of profit and it being surplus to expenses. Distinction between businesses with immediate or gradual incomes is meaningless too.