SEBI Cracks Down on Alleged Manipulation of the Sensex Closing Auction Session
Key Takeaways
- •SEBI has accused Copthall Mauritius and Mansi Share of using aggressive buy and sell orders during the Sensex Closing Auction Session to influence the index's closing level.
- •The regulator estimates combined alleged wrongful gains of ₹3.68 crore (approximately ₹36.8 million) linked to expiry-day options positions held by the entities.
- •Benchmark closing levels feed index fund and ETF net asset values, mark-to-market valuations, and performance benchmarking, which is why end-of-day price distortions are treated as a market-integrity issue.
- •The allegations remain unproven accusations at this stage, and any SEBI directions could be appealed before the Securities Appellate Tribunal as enforcement proceedings progress.
- •Expiry-day activity in Indian index derivatives has faced increased scrutiny, including SEBI's 2024 restriction of weekly expiries to one benchmark index per exchange.
The Securities and Exchange Board of India (SEBI) has cracked down on an alleged manipulation of the Sensex Closing Auction Session (CAS), accusing Copthall Mauritius and Mansi Share of influencing the benchmark index's closing price.
According to the regulator, the two entities placed aggressive buy and sell orders during the CAS to move the Sensex's closing level and benefit from options positions they held on expiry day. SEBI has pegged the combined alleged wrongful gains from the activity at ₹3.68 crore (approximately ₹36.8 million).
The case was reported by CNBC-TV18 on August 19, 2026.
Background: SEBI is India's statutory capital markets regulator, established under the SEBI Act, 1992, with a mandate to protect investors and promote fair and transparent securities markets; it routinely investigates suspected manipulative and fraudulent trading practices. The Sensex is the flagship benchmark index of the BSE, tracking 30 large and liquid stocks. The Closing Auction Session is a dedicated end-of-day auction on the exchange through which closing prices are determined. Because expiry-day settlements for index options are based on the index's closing level, trading in the final auction is particularly consequential for derivatives positions.
The closing level of a benchmark index also matters beyond the derivatives desk: closing prices feed the net asset values of index funds and exchange-traded funds, mark-to-market valuations, and performance measurement against benchmarks, which is why distortions of end-of-day price discovery are treated as a market-integrity issue rather than a narrow trading dispute. Expiry-day activity in Indian index derivatives has faced stepped-up regulatory scrutiny in recent years; in 2024, SEBI rationalised weekly index derivatives by restricting weekly expiries to one benchmark index per exchange as part of a broader framework aimed at reining in speculative activity.
The allegations remain, at this stage, accusations by the regulator. SEBI enforcement matters typically proceed through investigative orders, show-cause notices, and directions such as disgorgement of alleged gains, with parties entitled to appeal before the Securities Appellate Tribunal; how this case advances will depend on subsequent regulatory or legal proceedings.
Source: CNBC-TV18
