Evan Schuman's StorefrontBacktalk

Customers of at least three major retail chains—including grocery chain Hannaford—found their credit and debit cards double-charged on Friday (Oct. 1), thanks to a First Data programming glitch and the processor’s attempt to fix it. The consumers weren’t only charged twice: the retailers were often paid twice.

The glitch happened on Oct. 1, but the ill-fated charges were rung up the day before, as is customary. “Settlement processing was delayed by several hours on Friday due to a technical issue. As a result, some cardholders saw duplicate charges and some merchants received duplicate funding for those transactions,” said a statement issued by First Data. “At this point, the issue has been reversed and duplicate charges are being refunded. Some cardholders should have seen the reversal as early as Sunday evening, but banks have various reversal processes, so some cardholders may experience a delay between the duplicate charge and the reversal on their statement.”

First Data Communications Director Glen Turpin said the incident impacted “multiple merchants” and also said he knew of three chains, but would only mention Hannaford. He wouldn’t describe the nature of the glitch—nor how it happened—other than to say that “it was not a system-wide thing.” Given the large number of chains the processor handles, it was clear that the incident did not impact the vast majority of chains in the network.

The most likely scenario is that a glitch of some kind halted transaction processing and that small portions of transactions were submitted to test whether repairs were successful. Some might have gone through when it appeared that they hadn’t, which would have caused the limited number of duplicate charges.

Given that the impacted transactions included both debit and credit charges from Visa and MasterCard, it could prove to be a powerful example of how much riskier debit cards are than their credit cousins, a lesson that Dairy Queen learned earlier this year.

Even if everything goes perfectly, a credit card double-charge will have little if any impact on the consumer. Once reported, a temporary credit gets issued, ultimately being replaced with a permanent credit. If that identical glitch happens on a debit card, the bank’s reimbursement of the funds is typically much slower because a bank’s reimbursement is much more “real money” than a card brand’s temporary credit.

Much worse, that consumer might bounce a large number of checks and face a lengthy list of legal as well as business consequences (car repossessed? Branded as a check fraudster?), not to mention all of those bounced check charges, both from the consumer’s own bank as well as the banks of people they have written checks to.

And, as Best Buy, Macys and even Starbucks discovered, it’s a lot easier for debit charges to glitch than it is for credit cards.