评估的税收收入能力与实际征收入库数之间的差额，称为税收收入流失度。 从理论上说，一定时期的税收总量是一个定数。实际操作起来，任何国家都不可能达到这个定数，也就是说税收收入流失度是固然存在的。为了说明税收收入流失度的大小，在这里我们引进税收收入流失率的概念， The difference between the estimated tax revenue capacity and the actual storage fee is called the tax revenue loss rate. In theory, the total tax revenue over a certain period is a fixed number. In actual operation, it is impossible for any country to reach this limit, which means that the loss of tax revenue does exist. In order to explain the magnitude of the loss of tax revenue, here we introduce the concept of tax revenue loss rate,