After receiving an inventory order that has items from a company promotion, in many cases, those special part numbers are handled as prepacks and will automatically disperse the items included into their regular part numbers (sometimes they are handled as sets that can be manually split).

When invoicing a customer, you'll want to use the regular part numbers (not the special promotion part numbers) for the items included in the promotion, and then apply any discounts off the regular retail price.

By handling it this way, your Gross Receipts tax report will accurately reflect the discounts you gave and your customer's product purchase history will also accurately reflect the actual items being purchased by your customer.