In reality, "Gift Vouchers" in any electronic store are no more than a negotiable credit balance... In effect, someone is paying in advance, for products that are to be delivered at a later date.

So GV's are actually a payment method - NOT, as is believed, a PRODUCT.

Additionally - and unlike "paper-based" vouchers, these electronic vouchers are fully negotiable instruments (just like cash), either in their entirety, or as segments.

I can buy a GV on a zencart shop for £100 and then "split it up" into Ten £10 portions and send these to 10 different people. (Each portion then assumes a new ID code). These recipients can do the same, and each time a bit is split off the amount, a new code is generated.

In a "real" shop, you are doing a similar thing, but not on such a dynamic level. When you sell a paper-based voucher in your shop, you are actually selling a "credit balance" against stock to the same value. The voucher is nothing more than a redemption note - just like a banknote. The only difference is that I buy a £100 paper voucher, I cannot cut it up into ten equal portions of £10.

... but even so, the paper voucher is just like its electronic counterpart - a form of payment and not a product or object.

The only way round this is to examine discount vouchers as these can have a unique number, and be applied to unique situations.