Volume or Settlement Discounting
Suppliers may offer customers discounts for either achieving a minimum threshold of purchases (Volume discount) or for prompt settlement of outstanding receivables (Settlement discount). 
In order to calculate the appropriate revenue to be recognised, it may be necessary for an entity to estimate the volume of sales or the expected settlement discounts for an entity to estimate the volume of sales, or the expected settlement discounts to be taken. 
The revenue recognised would then be reduced by this estimate, such that the revenue recognised represents the fair value of the right to consideration. 
The need to estimate the amount of discounts expected to be taken does not preclude the reduction of revenue for these discounts. 
However, if no reliable estimate can be made then the revenue recognised on the transaction should not exceed the amount of consideration that would be received if the maximum discounts were taken