India beats a hasty retreat from a crucial market reform
The Securities and Exchange Board of India (SEBI) had directed stock exchanges to determine the end-of-day closing price of roughly 200 derivative-linked stocks through a final 20-minute call auction, introduced in early August 2026.
The reform was intended to curb "marking the close" — a manipulative practice where large traders push prices up or down in the last few minutes of continuous trading to distort the official closing price, which is used to settle derivative contracts.
Within about a month, the mechanism drew sharp criticism: intraday price trends reportedly reversed abruptly inside the 20-minute auction window, and volatility in options linked to these stocks increased, with market participants calling the design unworkable.
SEBI has since issued a consultation paper proposing two alternatives — shortening the auction window, or suspending the call-auction method for derivative-linked stock settlement for at least a year and reverting to the earlier method of averaging prices over the last 30 minutes of continuous trading.
Analysts have linked part of the reform's difficulty to high Securities Transaction Tax (STT) rates, which discourage arbitrageurs who would otherwise trade against the auction's price swings and stabilise prices.
Call Auction Mechanism and Closing Price Determination
A call auction is a price-discovery method where all buy and sell orders placed within a fixed window are collected and matched at a single equilibrium price (rather than continuously, order-by-order, as in normal trading), commonly used at market open/close specifically to reduce the influence of last-moment, high-frequency order flow on a benchmark price. India's stock exchanges have historically calculated the closing price as the volume-weighted average price over the last 30 minutes of continuous trading, a method vulnerable to "marking the close" manipulation because large late orders can skew the average.
Key Details
- SEBI's August 2026 circular mandated the auction method be applied specifically to stocks with an active derivatives (futures & options) market, since the closing price of the underlying stock is used to cash-settle or mark-to-market these contracts.
- Call auctions are already used in Indian markets at the pre-open session (9:00–9:08 am) for equities and in the periodic call auction mechanism for illiquid securities, so the reform extended an existing, tested mechanism to a new use-case (closing price) rather than inventing a new tool.
- The core trade-off exposed by the episode: a call auction reduces manipulation risk from continuous-trading order flow but concentrates trading into a short window, which can itself produce sharp price swings if liquidity (including arbitrage activity) is insufficient during that window.
The reform's rollback illustrates that a manipulation-resistant mechanism can fail in practice if market microstructure conditions (liquidity, arbitrage capital) are not designed for it — SEBI's proposed climbdown (shorter window or reversion to the 30-minute average) is a direct response to this liquidity mismatch.
SEBI's Regulatory Powers and Anti-Manipulation Framework
SEBI derives its power to regulate securities markets, including issuing binding directions to stock exchanges on trading mechanisms, from the Securities and Exchange Board of India Act, 1992. Market manipulation and fraudulent trade practices, including price manipulation around the close, are separately governed by the SEBI (Prohibition of Fraudulent and Unfair Trade Practices relating to Securities Market) Regulations, 2003 (PFUTP Regulations), whose Regulations 3 and 4 prohibit fraudulent devices and manipulative practices affecting security prices.
Key Details
- Section 11 of the SEBI Act, 1992 empowers SEBI to take measures to protect investor interests and regulate the securities market, the statutory basis for circulars such as the closing-price auction mandate.
- Under the PFUTP Regulations, SEBI's Whole Time Members can order disgorgement of illicit gains, trading suspension, or market debarment, while adjudicating officers can levy monetary penalties for violations — separate from SEBI's power to prescribe market-structure rules like the auction mechanism.
- SEBI's willingness to revisit or roll back its own circular within weeks reflects its regulatory practice of issuing rules via circulars/consultation papers (subordinate to the Act and Regulations) rather than amending primary legislation, allowing for faster iteration.
The closing-price auction was a SEBI circular-level intervention aimed at strengthening the practical enforcement of PFUTP's anti-manipulation intent; its rapid reconsideration shows the regulator using its own subordinate rule-making flexibility to correct an unintended consequence rather than needing legislative change.
- The call-auction closing-price mechanism was introduced by SEBI in early August 2026 for approximately 200 derivative-linked stocks.
- India's prior closing-price method was the volume-weighted average price over the last 30 minutes of continuous trading.
- SEBI's consultation paper proposes either shortening the auction window or suspending the mechanism for at least one year for derivative-settlement purposes.
- The PFUTP Regulations, 2003, framed under Section 11 of the SEBI Act, 1992, are the legal basis for treating "marking the close" as prohibited market manipulation.