The Securities and Exchange Board of India (SEBI) has declared an end to the back-and-forth adjustments of expiry days between the National Stock Exchange (NSE) and the Bombay Stock Exchange (BSE) for equity derivative contracts. SEBI Chairman Tuhin Kanta Pandey announced on Wednesday, June 18, 2025, that there would be no further changes to the derivatives expiry day. This decision concludes a period of speculation and numerous shifts by the bourses.
The changes, set to take effect on September 1, 2025, will see NSE moving its weekly expiry to Tuesday, while BSE will shift to Thursday. This adjustment follows SEBI's directive issued on May 26, 2025, which mandated that all equity derivative contracts (weekly, monthly, quarterly, and semi-annual) must expire on either Tuesday or Thursday. The primary aim is to prevent both exchanges from having expiries on the same day, thus reducing market congestion and promoting more orderly trading activity.
The expiry day war between NSE and BSE began in May 2023, with BSE introducing Friday expiries. NSE responded by moving its Bank Nifty expiry to Wednesday, and BSE countered by shifting its Bankex expiry to Monday in October 2023. In January 2025, BSE further altered its Sensex expiry to Tuesday, resulting in increased volumes. However, these frequent changes raised concerns at SEBI regarding growing volatility and speculative trading, leading to the regulatory intervention.
According to analysts, NSE is likely to benefit significantly from the new arrangement. With the Tuesday expiry, NSE will enjoy three full days (Friday, Monday, and Tuesday) of heightened options trading activity leading up to its expiry, which is a crucial period for premium buildup and speculative action. In contrast, BSE's Thursday expiry leaves a narrower window for pre-expiry speculation, particularly with Wednesday often dominated by NSE's midweek expiry dynamics.
BSE's market share is potentially at risk due to this shift. Motilal Oswal Financial Services Ltd. noted that BSE's share of the premium turnover market stood at 22.6% in May. Analyst Prayesh Jain has downgraded BSE's stock from "buy" to "neutral" and cut the bourse's earnings estimate by 9% for the financial year ending in March 2026, anticipating a loss in market share for BSE in terms of premium turnover.
In addition to the expiry day changes, BSE will cease launching new weekly index futures contracts from July 1, 2025. Existing contracts expiring on or before August 31, 2025, will maintain their current expiry schedule, while contracts expiring on or after September 1, 2025, will shift to Thursday. Monthly contracts will expire on the last Thursday of each month, starting September 1, 2025.
For investors and traders, these changes will alter the rhythm of the week. NSE's new Tuesday expiry means longer premium buildup periods, increased liquidity, and higher open interest leading into expiry, which is advantageous for short-term F&O traders. The move is seen as balancing market stability while reinforcing NSE's dominant position in the derivatives space, potentially dampening BSE's momentum in growing its relatively newer options segment. SEBI's intervention aims to bring more order to trading activity, improve risk management, and enhance market participation across both exchanges.
