Applying Discounts
When viewing a profile from a constituent record, select Make Payment underneath the Balance Due section. In the payment window, select which line item you need to discount.
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If you select one of the preset discounts, the discount will automatically apply to the payment. If you enter a unique discount, select Apply to process the discount.
When any amount of line items are selected, and the discount is 100%, the only option is to clear the invoice. In this case the Process Discounts button will become available. Select it to clear the line items off of the invoice.