S.Korea fines Citadel Securities for stock algorithm trading breaches

A person walks by the Citadel Securities offices on Park Avenue in Manhattan, New York City

SEOUL (Reuters) - South Korea's financial regulator has imposed a fine of 11.88 billion won ($9.66 million) on U.S.-based Citadel Securities, saying it disturbed the local stock market with high-frequency algorithm trading.

The Financial Services Commission (FSC) said in a statement released on Thursday the firm had distorted stock prices with artificial factors, such as orders on the condition of "immediate or cancel" and by filling gaps in bid prices.

The firm carried out such trading on an average of 1,422 stocks per day from Oct. 2017 to May 2018, totalling more than 500 billion won worth of trades, according to the statement.

The Commission said it was the first time it had imposed fines on such high-frequency trading on the South Korean stock market, which has a high proportion of retail investors and little competition among algorithmic traders.

It added the firm did not provide algorithm source codes in the consultation process.

The regulator declined to identify the brokerage in violation but Citadel Securities confirmed it had been awaiting a decision, although it had yet to hear directly from the Commission.

"Citadel Securities works diligently to follow all applicable laws, regulations, and rules in jurisdictions in which we trade," it said in a statement. "We strongly believe our trading complied with both Korean laws and global norms. We disagree with the FSC’s decision relating to our trading activity more than five years ago and will be seeking to appeal the decision."

Citadel Securities was surprised and concerned to see that the regulator's findings include references to a number of hearings the firm itself was not invited to participate in and supposed expert evidence that was never shared with the company and that it never had an opportunity to respond to, a source familiar with the situation said.

($1 = 1,229.7200 won)

(Reporting by Jihoon Lee; Editing by Lincoln Feast.)