The average profitability of a particular sector and its relationship to specific factors and indexes were discussed with representatives of the sector before the official tahshiv was issued. The elaborate preparation and continual updating of the tahshiv required considerable time and effort by the revenue authority, defeating the goal of simplicity intended by many presumptive tax schemes. Nevertheless, due to widespread use and well-designed taxation system, the contribution of income taxes to tax revenues in Israel is among the highest in developing countries. The estimated assessment method of presumptive taxation employs a variety of techniques to derive taxpayer income, both simple and complex. Simple methods are based on single factors such as a taxpayer's total assets, net wealth or value of business assets, gross receipts of business, and visible signs of wealth.
Complex methods use factors and indices of profitability, which vary by economic activity.
As a result, governments that tax agricultural output have adopted laws that assess income based on potential output of land or crop yield, as well as soil quality and productivity ratings. For example, Armenian citizens involved in agricultural production are exempt from profit tax on sales of their agricultural products. However, they are subject to land tax based on the government-issued financial cadastre, which values agricultural land for the purposes of taxation. As one can imagine, it is difficult to determine the amounts at the beginning and end of the year with any precision, much less account for expenditures during year. Thus, tax authorities in developing nations such as Argentina, Chile, and Colombia employ this method as a basis for presuming income during audits.