Jérôme Kerviel’s unauthorized trading caused Société Générale a loss of about €4.9 billion in 2008. It was one of the largest losses ever attributed to a single rogue-trading episode.
Kerviel worked in Société Générale’s Delta One division, where he traded equity derivatives and related products. According to the bank, he began creating fictitious transactions to conceal increasingly large unauthorized positions. The trades initially appeared profitable, but the hidden exposure became enormous as markets turned against him.
Société Générale discovered the positions in January 2008 and closed them over several days. The unwinding coincided with a sharp fall in global equity markets, crystallizing the €4.9 billion loss. The bank announced the loss on January 24, 2008, and sought billions of euros in new financing to strengthen its balance sheet.
Kerviel was convicted in France of breach of trust, forgery, and unauthorized use of the bank’s computers. The case also prompted debate about Société Générale’s internal controls and whether responsibility rested solely with the trader. The €4.9 billion figure refers to the bank’s trading loss, not a personal amount Kerviel possessed or stole.