India’s introduction of a new closing auction system has led to sharp swings in stock prices during the final minutes of trading, raising concerns over liquidity and impacting index derivatives, as traders and brokers adjust to the disrupted market dynamics.
India’s index-options market may face a bumpy adjustment after the introduction of a new closing auction system that has stirred sharp late-session swings in stock prices and unsettled traders, brokers and exchanges. Reuters, citing Bernstein, reported that the change is likely to pressure trading volumes and shares linked to capital markets in the near term, even if the market eventually adapts over the coming months.
The Securities and Exchange Board of India began rolling out the closing auction session on August 3, with the aim of setting a single, more reliable closing price for eligible shares in the cash market. The National Stock Exchange also extended equity derivatives trading to 3:40 pm to align with the new mechanism, which is intended to improve price discovery and bring Indian markets closer to global practice.
For index derivatives, the change matters because the official closing prices of stocks with futures and options contracts can feed into benchmark levels such as the Nifty 50 and Sensex. That makes the final minutes of trading especially important for options traders, whose positions can be revalued sharply if index levels move at the close.
Bernstein’s analysis suggests the biggest impact has been a collapse in activity during the last 15 minutes of the session. Trading in that window has fallen to about 1.6% to 2.3% of daily turnover on the NSE, far below a historical average of 10.1%, leaving thinner liquidity and making prices more vulnerable to relatively small orders. The research firm said that has made the closing period harder to read for market participants.
Bernstein analysts Manas Agrawal and Himank Sangai said the closing auction has become a major topic among investors because of its effect on volumes. The firm also flagged concerns about unusual price action during the auction window, raising the possibility of spoofing, a practice in which traders place orders without intending to execute them to influence prices. Passive funds have so far largely stayed out of the closing window, though they may be forced to participate on days when benchmark indices are rebalanced.
The impact may extend beyond traders. Lower index-options turnover could weigh on discount brokers that depend heavily on retail trading activity, while exchanges could also feel the squeeze because they earn fees from options premium turnover. Bernstein expects the system to settle as market participants adapt, but for now the transition appears likely to keep the final stretch of the trading day more volatile and less predictable.
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