The Problem
This is mainly a question of Uniqueness. We need to ensure that vouchers are legitimate and can only been used once.
Retail vouchers can be very low value - 1 or 2 pence is not unusual. So the solution must be near zero cost per voucher.
They may not be unique - there can be millions of identical "5p off a tin of beans" vouchers. The uniqueness, therefore, must be added.
They often have qualification criteria and can only be used if the accompanying purchase meets the relevant criteria. For example, they may have expiry dates and only be valid up till that date; and/or they have activation dates and only be usable from that date. They may be tied to specific products and quantities. (eg buy one get one free)
They usually have limited retail validity - can only be used in specified stores or a specified chain.
Some may NOT have limited retail validity - the voucher may be issued by the brand owner, not the supermarket and thus qualify in ANY store selling the brand. These stores may all have radically different Point of Sale software.
The vouchers are typically used at the checkout. This means that the process of validation what may be multiple vouchers must take less than, say, 30 seconds and take place - once scanned - in the background while the customer is packing goods or credit cards are being authorised etc.
The Codel Solution
Add a Validation Reference to each voucher at the time of printing (or overprint later). Many vouchers already use serial number like unique identifiers and the VR is merely a technically more secure version of that identifier. In such cases, the VR will impose no significant additional cost. Only in cases where no existing Unique identifiers are used, will significant new costs arise. With modern digital printing techniques, the unit costs of printing unique VRs on 10,000 or 10 million labels are effectively negligible.
The only problem is the "real-time" validation of the voucher. Few retail outlets have permanent web or even WAN connections. Where neither exists, the voucher data will need to be stored and checked in a batch process overnight.
Alternatively, if the stores runs its own WAN but cannot easily be connected to the web, the stores can download the Valid Voucher list overnight and run local validation during the day. Then upload the results at night and check for any collisions. There is a finite risk that counterfeits are being used in other similar locations during the day which won't be detected until the upload at the end of the day but for low value items the probability of counterfeit is low and the prospective losses are low. The economic risk is, therefore, minimal.
For the higher value vouchers, the simplest and cheapest solution is a dedicated web terminal. A single terminal at the "Customer Services" station could, for example, validate the voucher for the customer prior to their shopping and either issue a local one day token of equivalent value or endorse the voucher with a one day pass.
Flowchart
Powerpoint
