The Commerce Department requires the calculation of adjustments to reflect all discounts that are not reflected in the net invoice price. The starting point for all sales is the net invoice price. Accordingly, if the discount is granted at the time of payment (as a reduction in the amount due), an adjustment needs to be made. If the net invoice price already reflects a discount, however, no further adjustment is warranted. The Commerce Department defines 'rebates' as payments or credits made to customers after the invoice has been issued. All rebates to the customer must be accounted for.

The Commerce Department prefers that discounts and rebates he tied to specific invoices. The calculation methodology for calculating invoice or model specific discounts and rebates depends on how they are granted and recorded on the company books. If such incentives are granted as a fixed percentage of the sales price, the company should calculate the adjustment by multiplying this percentage factor by the unit price of the product.

Source: Business Guide to Trade Remedies in the United States: Anti-dumping, countervailing and safeguards legislation practices and procedures