By Jayshree P Upadhyay

MUMBAI (Reuters) -India has barred one of the world's largest quant trading firms, Jane Street, from accessing its securities market after an investigation found it made "unlawful gains", taking the most stringent action ever against a foreign trading firm.

The markets regulator also impounded $567 million from U.S.-based Jane Street, which said it disputed the findings. Here are facts about Jane Street and its India presence:

WHAT IS JANE STREET?

Jane Street has more than 3,000 staff in five offices across the United States, Europe, and Asia. It trades in stocks of 45 countries and is also rapidly increasing its presence in Hong Kong by purchasing more office space.

Jane Street was established in 2000 and its annual revenues last year were $20.5 billion.

It describes itself on its website as a firm that uses "sophisticated quantitative analysis and a deep understanding of market mechanics" to keep prices consistent and reliable."

"We're a firm of puzzle solvers on and off the clock," it says.

HOW DOES JANE STREET OPERATE IN INDIA

Jane Street operates in India through four group entities, two of which are based in India, with the other two in Hong Kong and Singapore.

The firm started its first India unit in December 2020. The other two Asian entities operate as foreign investors registered with India.

THE SCALE OF ITS INDIA OPERATIONS

Between January 2023 and March 2025, the four entities cumulatively made a profit of $5 billion by trading in equity options in India, the country's market regulator SEBI said in its order.

Jane Street's large India presence first gained prominence last year when the firm sued a rival hedge fund, Millennium Management, accusing it of stealing a valuable in-house trading strategy.

At a court hearing in the U.S., it was revealed that the strategy involved India options and had generated $1 billion in profits for Jane Street in 2023. The two firms settled the case in December.

JANE STREET'S INDIA CHALLENGE

India's market regulator says Jane Street as a group first aggressively bought significant quantities of banking stocks and futures, temporarily pushing up the banking index.

Later, it aggressively sold large quantities of the same banking stocks and futures.

This large scale buying influenced retail investors to invest, leading to market manipulation, SEBI said.