When selling gift cards online, there are two major workflows to consider:

In both scenarios, the gift card has a unique ID printed on the face that acts as a Gift Code. Typically, the Gift Code ID is concealed throughout the card's lifecycle by a scratch-off covering. In addition to the Gift Code, the card packaging will also contain a UPC and/or SKU for inventory tracking in the supply chain.

For Activation Required programs, the IDs printed on the card are inert until approved by the retailer. In addition to the concealed Gift Code, a serial number is printed as a barcode on the card's packaging. A database is kept that relates card Serial Numbers to Gift Codes. Upon approval by the retailer, the Serial Number is used to look up the Gift Code and the Gift Code is marked as "ready for use" in the retailer's POS system. 

Even though the Gift Codes are inert through the early stages of the lifecycle, they remain covered until after the sale to prevent a type of fraud wherein Gift Codes are captured while inert and held until they become activated by a legitimate sale.

In Whiplash, the Gift Cards must be sold in pre-determined denominations. The item will be flagged with Serial Number Required. When orders are shipped for the gift card item, operators are required to scan the Serial Number, which will be attached to the order and visible to the retailer. This allows the retailer to Activate the Gift Code before the receiver attempts to redeem it.

In this scenario, simple possession of the card is the only verification required, as all Gift Codes are added to the retailer's POS during manufacturing. Cards are sold in specific denominations and treated the same as any inventory item.

Related Questions:

What are the two major workflows for Gift Cards?