Thousands of consumers were charged twice due to an issue with a particular card terminal run by Cardnet, a joint venture between Lloyds Bank and First Data.
Money came out of bank accounts twice but transactions only showed up once on many shop, pub and restaurant receipts.
Lloyds Banking Group said just under five percent of Cardnet machine transactions were affected on part of 29 August and all affected customers had been refunded.
People banking with other organisations were charged twice for spending money in shops, restaurants and businesses using Cardnet terminals as their way of taking payment.
Most of the affected transactions involved Visa debit cards.
Cardnet said in a statement: “On Friday September 1, Cardnet became aware of an incident whereby the settlement file for transactions taken Wednesday August 29 by APACS 40 (standalone terminal) merchants was duplicated and the settlement file for transactions taken Thursday August 30 was consequently not submitted.
“This has resulted in merchants receiving incorrect settlement amounts, based on both the duplicate file and late payment of Thursday’s funds. In some cases, this will have been an overpayment of expected settled funds, in others an underpayment. In addition, and importantly, cardholders (customers) of Cardnet’s impacted merchants may also have been debited twice for transactions made on Wednesday.
“Both Thursday’s settlement file and the reversal of duplicate transactions has been sent for processing, which will correct the issue for merchants as part of their settlement of funds from Friday 1st September and bring their settlement back into line of what is expected within two days. We anticipate that refunds to cardholders charged twice will be completed by Tuesday 4th September.
“Cardnet sincerely apologises for the issue and the inconvenience caused, we continue to work closely with all parties to resolve this issue swiftly.”