Why was taking revenues not possible …

Todar Mal was Akbar’s revenue minister. He carried out a careful survey of crop yields, prices and areas cultivated for a 10-year period i.e. from 1570 to 1580. Based on this data, tax was fixed on each crop in cash. Each province was divided into revenue circles. Each circle had its own schedule of revenue rates for individual crops. This revenue system was called zabt. It was prevalent in the areas where Mughal administrators could survey the land and keep very careful accounts. But it was not possible in provinces; such as Gujarat and Bengal. The zamidars exercised great deal of power in some areas. Their exploitation by Mughal administrators forced them to rebel against it. These revolts collectively by zamindars and peasants challenged the stability of the empire from the end of the 17th century.