A method, system, and computer usable program product for pre and post purchase identification of counterfeit products in a supply chain are provided in the illustrative embodiments. A customer reference number (CRN) associated with a unit of product is identified. The unit of product has associated therewith a unique set of identifiers including the CRN, a customer acknowledgment number (CAN), and a merchant acknowledgment number (MAN). The CRN is sent to a second application and a message is received from the second application in response to sending the CRN. If the message includes a second CAN that is not the same as the CAN associated with the unit, the unit is determined to be a counterfeit product.