Evan Schuman's StorefrontBacktalk

Indeed, Best Buy refunded Williams for the extra charges. Williams said the retailer also promised it would send him a $75 check to pay for penalties he was accessed by the bank in the days after the incident because several of his checks, including one for a car payment, bounced.

Best Buy Stands By Its Statement

In an interview conducted before Best Buy decided to merely “stand by” its statement, Nezworski said she thought the cashier’s second and third swipes of Williams’ card “were incorrect” as a store practice. However, she also said the transaction wasn’t allowed to go through until after the store contacted Visa and received an authorization.

Orrock said he could envision several explanations for Williams’ experience, and most of those explanations “have to do with error codes being properly translated.” Perhaps the acquirer might have received a code from a system in the middle saying the transaction was taking too long and timed out. He said the message that Williams exceeded his daily limit, an unusual message for a POS to see, could have been caused by a mistranslation of the ‘response code’ as the message is passed back from institution to institution.”

As for the systems designed to watch for and prevent these kinds of duplicate charges, those systems are only as effective as the data they are allowed to access. Orrock said, for example, that payment processing systems rarely check product codes to see if the same product is being paid for multiple times. “I build some big POS systems and we are not checking SKUs,” Orrock said. “We are not checking product codes. Payment switches are not getting down to that level.” He also noted that, if the first attempted transaction was recorded by Best Buy as a denial of some sort, but approved by the issuer, the system would not see a subsequent attempt as being a duplicate because it thought the first one was rejected.

The Best Buy system might have done everything properly but could have been dealing with garbled information from somewhere else in the complex process. “What (codes) the issuer passes back and what ends up at the POS can sometimes be entirely different,” Orrock said. “A lot of things have to right for that to work. My 2-digit codes might not be the same as the next guy in the chain. You’re dependent on everybody making the right translations.”

While not particularly commonplace, Orrock said PIN debit system hiccups are not totally rare, especially when store clerks swipe cards multiple times. “You do see situations like this where, for one reason or another, all the actors involved in the transaction did not discharge their duties properly,” Orrock said. “I could concoct a scenario for you that fits what happened to this guy with absolutely no problems evidenced by Best Buy. Best Buy could be totally in the dark, in a good way, about what happened. They would get something back that indicates the transaction was rejected or denied. They get a response code and throw it on screen. In the meantime, behind the scenes, the issuer authorized the transaction.”

Orrock urged retailer CIOs to “pay attention” to their systems suspense file. “What ends up happening in debit is, you typically provide the gateway with a list of all the transactions you think you consummated during the day and the gateway is going to match those transactions up. If there are any differences between the file you sent and what the gateway processor thinks they processed online, those items are going to fall out and go to the suspense report. You must pay attention to the items on there, the spurious items.”