Nasdaq Helsinki’s Disciplinary Committee has fined Citigroup Global Markets Europe AG €350,000 following a catastrophic fat-finger trading error that caused a temporary but sharp market collapse across the Nordic region.

On May 2, 2022, a Citi trader accidentally submitted USD 444 billion worth of sell orders, misentering 58 million units instead of €58 million. Although Citi’s internal controls caught part of the order, approximately USD 190 billion worth of erroneous orders passed through its algorithmic trading system and began executing.

Within minutes, markets in Finland, Sweden, and Denmark dropped by up to 8%. Citi did eventually halt the trades, but only 13 minutes later-and Nasdaq was only formally informed over 30 minutes after the initial event.

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Controls Overridden, Systems Failed

The committee concluded that pre-trade control systems were inadequate, particularly given that the trader was able to override multiple system warnings and continue placing high-risk orders. While Citi did enhance its controls post-incident, that wasn’t enough to mitigate the regulatory breach.

Moreover, Nasdaq criticized Citi’s delayed communication and outdated contact details, which made coordination during the market disruption even more difficult.

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Operational Risk in Focus

This incident exposes deep vulnerabilities in manual order entry, algorithmic execution, and real-time monitoring systems. A single trader, acting alone, was able to disrupt an entire region’s market-demonstrating how operational lapses, even unintentional ones, can become systemic events.

The fine may be symbolic relative to Citi’s scale, but the reputational and structural impact speaks volumes. For firms with algo exposure or high-volume operations, robust internal controls are no longer optional-they're critical to market integrity.

Stay tuned. PropInsider continues to monitor enforcement actions and market incidents that redefine how operational risk is managed in modern trading environments.

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