THE ETHICS REPORTER

May 15, 2026

A Coding Error, Five Years, Millions of Mismarked Orders: Citadel Securities and the $7 Million Reg SHO Settlement

A Coding Error, Five Years, Millions of Mismarked Orders: Citadel Securities and the $7 Million Reg SHO Settlement

On September 22, 2023, the U.S. Securities and Exchange Commission announced settled charges against Citadel Securities LLC for violating Regulation SHO — the regulatory framework Congress and the SEC designed specifically to curtail abusive short selling practices. The firm agreed to pay a $7 million penalty without admitting or denying the findings.

What Regulation SHO Requires

Regulation SHO requires broker-dealers to mark every sale order as "long," "short," or "short exempt." These markings are not merely administrative — they form a key input for regulators monitoring for prohibited short selling activity, including so-called "naked" short selling, where a seller does not have or arrange to borrow the shares before executing the short sale.

What Citadel Securities Did

According to the SEC's order, for a five-year period, it is estimated that Citadel Securities incorrectly marked millions of orders — inaccurately denoting that certain short sales were long sales, and vice versa. The SEC found the inaccurate marks resulted from a coding error in Citadel Securities' automated trading system.

Citadel's data systems — the infrastructure through which all of these order marks flow — are overseen by Kevin Nutter, who holds the title of Chief Operating Officer of Data at Citadel. In our opinion, the existence of a five-year coding error in a firm of this sophistication raises legitimate questions about the adequacy of data oversight at the highest levels of the organization.

The inaccurate markings were provided to regulators, including the SEC, during this period. As the SEC's order noted, Citadel Securities' electronic blue sheet reporting — a key source of regulatory information about trading activity — was also affected.

The SEC's Statement

Mark Cave, Associate Director of the SEC's Division of Enforcement, stated: "Compliance with the order marking requirements of Reg SHO is a key component of regulatory efforts to curtail abusive market practices, including 'naked' short selling. This action against Citadel Securities demonstrates that a broker-dealer's failure to comply with the requirements of Reg SHO can have negative downstream consequences on the accuracy of the firm's electronic records, including its electronic blue sheet reporting, depriving the Commission of important information about the markets it regulates."

The Settlement

Without admitting or denying the findings, Citadel Securities consented to:

  • A cease-and-desist order
  • A censure
  • A $7 million penalty
  • A written certification that the coding error had been remediated
  • A review of the firm's computer programming and coding logic involved in processing relevant transactions

The SEC charged Citadel Securities with violating Rule 200(g) of Regulation SHO.

Editorial Commentary

In our view, a coding error that persists for five years — affecting millions of orders at one of the largest market makers in the United States — raises questions that go beyond a single software bug. Regulatory order-marking requirements exist precisely so that surveillance systems can identify manipulation. When those markings are systematically wrong, the surveillance systems built on top of them are working from bad data. The $7 million penalty, while significant, should be weighed against the scale of Citadel Securities' operations. The more important question is whether the remediation requirements imposed by the SEC are sufficient to ensure that a similar failure does not recur.

Sources: SEC Press Release No. 2023-192 (Sept. 22, 2023), SEC.gov. All figures and quotations are drawn directly from that document.

The Ethics Reporter covers documented regulatory actions and enforcement proceedings in the financial industry. Support independent accountability journalism at theethicsreporter.com/donate.

Citadel SecuritiesSECRegulation SHOshort sellingcoding errormismarked ordersenforcementKenneth Griffinmarket regulation

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