Discount rules may be edited manually on individual repair order, sales invoice, and credit note records. To edit discount tax rules, either right-click on the scroll buttons of the discount rate field, or press the Alt+ key combination while in the discount rate field. A popup window will appear listing the additional discount rules which may be selected.
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Check or uncheck the desired discount rules and then either click on any field outside of the popup window, or press the Alt+ key combination to close the window.
See Taxes for a complete discussion of working with taxes on repair orders, sales invoices, and credit notes.