India’s market watchdog last week barred quantitative trading firm Jane Street Group and its local affiliate from the nation’s securities markets after a 105-page interim order alleged the firm manipulated index derivatives to reap a net gain of about Rs 36,500 crore between January 2023 and March 2025. The Securities and Exchange Board of India (Sebi) also ordered the disgorgement of Rs 4,840 crore in alleged unlawful profits, froze the entities’ Indian accounts and gave the firm 21 days to file objections. Former Sebi chair Madhabi Puri Buch said the enforcement action was the result of a probe that began as early as April 2024, countering media suggestions that regulators acted too late. Buch detailed how a multidisciplinary team examined complex trading structures and that the National Stock Exchange had issued a cease-and-desist letter to Jane Street in February 2025. She described claims of regulatory failure as a “false narrative.” According to Sebi’s order, Jane Street booked roughly a $1 billion loss in single-stock futures while generating about $5 billion in options gains through strategies that pushed Bank Nifty prices higher intraday and then profited from the reversal. The Economic Times estimated that retail derivatives traders lost nearly Rs 1 lakh crore during the period. The case has rattled India’s Rs 6 lakh-crore derivatives market. Zerodha co-founder Nithin Kamath warned that the episode exposes systemic risks for brokers and exchanges, while analysts said the investigation may prompt tighter surveillance of algorithmic trading and expiry-day price moves.