Citadel Securities

In 2002, Ken Griffin and his partners founded the market maker Citadel Securities in Chicago, a dozen years after he founded the hedge fund Citadel there in 1990. Citadel Securities LLC, the legal entity that operates the business, was formed in Delaware on July 30, 2001, was approved by the US Securities and Exchange Commission for registration as a broker-dealer on April 17, 2002, and became a FINRA member on February 25, 2005.⁠[1][2][3][3][3]

On January 13, 2017, the US Securities and Exchange Commission announced that Citadel Securities had agreed to pay $22.6 million to settle charges that its Citadel Execution Services unit, which handled retail orders from other brokerage firms, misled customers, including $5.2 million in disgorgement plus interest and a $16 million civil penalty. The SEC found that the unit had implied to its broker clients that it would internalize their orders at, or seek in the market, the best price it observed across its market data feeds, but that two algorithms, known as FastFill and SmartProvide, did not do so, in violation of Section 17(a)(2) of the Securities Act. At the time, Citadel Securities executed about 35% of the average daily volume of retail equity shares traded in US markets.⁠[4][3][3][4][4][4][3][4]

In March 2017, Peng Zhao became CEO of Citadel Securities. He joined the firm directly out of graduate school as a Senior Quantitative Researcher and was one of its early architects; he earned his PhD in Statistics from the University of California, Berkeley, and his bachelor’s degree in applied mathematics from Peking University.⁠[3][5][5]

On December 10, 2018, the SEC found that all 2,774 electronic blue sheets Citadel Securities submitted to the SEC from November 2012 to August 2016 contained deficient information, resulting in incorrect reporting of trade execution time data for approximately 80 million trades, in violation of the recordkeeping and reporting requirements of the Securities Exchange Act; the firm was censured and paid a $3.5 million civil penalty.⁠[3][3][3]

On July 16, 2020, FINRA found that Citadel Securities had failed to establish a reasonable supervisory system to ensure that OTC customer orders complied with the rules on trading ahead and limit order display; without admitting or denying the findings, the firm was censured and fined $700,000, and was required to pay restitution plus interest for customer orders it executed at prices worse than those at which it traded for its own account.⁠[3][3][3]

During the concentrated retail trading in GameStop and other “meme stocks” in late January 2021, Citadel Securities executed 7.4 billion shares for retail investors on January 27 alone, more than the average daily volume of the entire US equities market in 2019. On February 18, Griffin testified before the US House Financial Services Committee as founder and principal shareholder of Citadel Securities, saying that Citadel Securities was the largest market maker in the US equities market and executed more trades on behalf of retail investors than any other firm; he said the firm had no role in Robinhood’s decision to restrict trading in GameStop and other stocks and learned of the restrictions only after they were publicly announced.⁠[1][1][1][1][1][1]

In December 2021, Citadel Securities reached a collective settlement with 13 exchanges operated by Cboe, Nasdaq, and the New York Stock Exchange. The exchanges found deficiencies in its pre-trade erroneous order price controls; for example, price controls were not applied to equity limit orders that had been canceled and replaced, and its procedures for manually reviewing “soft block” alerts lacked sufficient detail. The firm was censured and fined and agreed to revise its risk management controls and supervisory procedures; the fine imposed by the Cboe EDGX Exchange was $30,000.⁠[3][3][3][3][3][3]

On January 11, 2022, Citadel Securities announced that Sequoia and Paradigm had made a $1.15 billion minority investment in the firm, with Sequoia leading the round and Sequoia partner Alfred Lin joining the board. Then-chairman Griffin said he looked forward to working with the two investors as the firm accelerated its growth; CEO Peng Zhao said the firm saw enormous opportunities to serve clients across more markets and products; and Paradigm co-founder Matt Huang said he looked forward to the firm extending its technology to more asset classes, including crypto. At the time, its institutional business served more than 1,600 clients, including many sovereign wealth funds and central banks.⁠[6][6][6][6][6][6][6][6][6]

On June 23, 2022, Griffin wrote to employees announcing that both the hedge fund Citadel and Citadel Securities would establish new headquarters in Miami, in a new tower being built on Brickell Bay, and would lease office space in the city in the meantime; the two companies then had more than 1,000 employees in Illinois and would maintain operations in Chicago. As of October 2026, Citadel Securities’ main office address was 830 Brickell Plaza, Miami.⁠[2][2][2][2][2][3]

On January 26, 2023, South Korea’s Securities and Futures Commission found that Citadel Securities (Hong Kong) Limited, an affiliate of Citadel Securities, had engaged in market disruption in 6,796 trading periods involving 264 stocks in its trading in the South Korean market between October 18, 2017, and May 24, 2018, and had also violated short-selling rules on several occasions, imposing fines of KRW 11.88 billion and KRW 1.1 billion. The company said it did not contest the short-selling findings but expected to appeal the market disruption findings; as of October 2026, the matter was listed as on appeal in FINRA records.⁠[3][3][3][3][3]

On September 22, 2023, the SEC found that a coding error in Citadel Securities’ order marking system caused delays in its calculation of net positions and went undetected for at least five years, until the firm discovered and corrected it during an internal compliance review in September 2020; millions of sell orders were estimated to have been erroneously marked, constituting a willful violation of Rule 200(g) of Regulation SHO. The firm was censured, ordered to cease and desist, paid a $7 million civil penalty, and agreed to comply with undertakings.⁠[3][3][3][3][3]

On October 9, 2024, FINRA found that between June 22, 2020, and August 28, 2024, Citadel Securities failed to report tens of billions of equity and option order events to the Consolidated Audit Trail (CAT) central repository in a timely or accurate manner; without admitting or denying the findings, the firm was censured and fined $1 million.⁠[3][3][3]

On August 20, 2026, NYSE Regulation found that Citadel Securities, as a designated market maker, had since March 2025 failed to establish a reasonable supervisory system for meeting its closing auction obligations, particularly regarding when to escalate potentially significant closing price dislocations following a trading halt; the firm was censured and fined $75,000.⁠[3][3][3][3]

On October 7, 2026, the New York retail proprietary trading startup Vest LabsVest LabsVest Labs is a New York–based trading technology startup that operates Vest Markets, a 24/7 venue for perpetual futures on stocks, indices, commodities, foreign exchange, and crypto assets, and offers “prop trading” accounts that let retail traders who pass an evaluation trade with company capital and share in the profits.Open the full entry announced a $13 million seed round led by Portal VenturesPortal VenturesPortal Ventures is a US venture capital firm founded by Evan Fisher in 2022 that focuses on the pre-seed stage in blockchain and crypto, with its main strategy being to lead first checks before product-market fit; in 2026, it led the $13 million seed round of the retail proprietary trading startup Vest Labs.Open the full entry; the individual backers included senior executives at Citadel Securities.⁠[7][7][7]

Citadel Securities describes itself as a technology-driven global market maker that provides institutional and retail investors with liquidity, pricing, and seamless front-to-back execution. As of October 2026, it was registered with the SEC, 29 self-regulatory organizations, and 15 US states and territories; it had more than 1,000 employees and provided liquidity on more than 120 venues across more than 35 countries.⁠[8][8][3][5]

In terms of ownership, Ken Griffin indirectly holds 75% or more of Citadel Securities LLC through entities including GFH CSEVA LLC; CEO Peng Zhao holds between 5% and 10%. The hedge fund Citadel and Citadel Securities were both founded by Griffin and have developed as separate companies. As of October 2026, FINRA records listed 76 regulatory event disclosures for the firm.⁠[3][3][3][2][3]

Citadel Securities: Official website: https://www.citadelsecurities.com/ (opens in a new window).⁠[8]

LinkedInLinkedInLinkedIn is a social networking platform for professionals. It was founded in 2002 by Reid Hoffman and others, launched in 2003, and listed on the New York Stock Exchange in 2011; after Microsoft acquired it for approximately $26.2 billion in 2016, it became a wholly owned Microsoft subsidiary. Its revenue comes from membership subscriptions, advertising, and recruitment solutions.Open the full entry: Public profile: https://www.linkedin.com/company/citadel-securities/ (opens in a new window)⁠[8]