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Amount / Rate Can Be Changed: This option determines whether the discount card will be deleted when the discount card is selected and the amount or rate is changed in sales invoice, dispatch and order. When this field is marked, the discount card is not deleted from the relevant line when the rate or amount of the discount applied to the receipt or invoice is changed.
Formula: The field used to record the calculation method of the sales surcharge. Since the parameters of the Formula field use arithmetical and logical operators, the operations are performed automatically, decreasing the error rate.
Parameters are used in calculations in order to apply graded surcharges. Logical operations are applied on the Formula field of the sales surcharge, and the defined surcharge is specified to be applied or not according to the selected criteria. The usage of functions along with parameters is critical for the generation of detailed surcharge calculation systems. The parameters and functions listed in the window accessed by clicking on "..." icon: