How are invoice totals calculated and incentives and credits applied?

Whiteflash offers a number of incentives and adjustments such as Customer Loyalty Credit for returning customers and Form of Payment Adjustment for payment by wire transfer. In addition we run special promotions from time to time on certain products. There is a specific and logical order by which pricing and invoice totals are calculated when these items are applicable.
There are basically three elements involved and they are calculated in sequence:
Pricing - Advertised Price
Incentives - Credits and Special Promotions
Form of Payment Adjustment (wire transfer)
Whiteflash offers 3% off the Final Price when payment is made by wire transfer. Final Price is calculated by Advertised Price less any applicable Incentives. Sales tax, if applicable, is calculated based upon Final Price and added to the invoice to arrive at Final Invoice Total.
*only the portion of the invoice paid by wire transfer will receive the Form of Payment Adjustment.
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