If you have negotiated a discount with a supplier this can be added and managed by selecting the relevant supplier. On the Supplier Details at the bottom right had corner there is an option to specify the percentage discount that you have arranged with this specific supplier.
Note: Updating the supplier discount with an Effective Date of '@ Opening Balance Date' will apply the agency discount retrospectively to tickets already completed by this supplier. If a new discount has only be recently negotiated then a new entry should be inserted in the table with a relevant effective date.
Discounts can be overridden with a monetary value completing a ticket. To do this select to option to override the agency discount and enter the monetary value.