India’s capital market ecosystem reacted sharply on February 6 after the Securities and Exchange Board of India issued a circular changing how margins will be calculated for calendar spread positions in single stock derivatives on expiry day. The rule, effective May 5, 2026, removes the margin benefit traders currently enjoy when holding offsetting positions across different expiries if one of those contracts is expiring that day.

The immediate market response was visible. The Nifty Capital Markets index fell over 2 percent in morning trade, while shares of Nuvama Wealth Management and Central Depository Services Limited declined more than 3 percent each. Broader selling pressure was also seen in exchange-linked and brokerage counters, including BSE Limited.

The regulatory change addresses a specific risk embedded in calendar spread trades. In this strategy, traders buy a long-dated futures or options contract and sell a near-term contract of the same strike, benefiting from the price differential between the two while enjoying lower margins due to the hedged nature of the trade. Until now, even on expiry day of the near leg, traders retained the lower margin requirement throughout the trading session.

What changes now is the timing of that benefit.

From May 2026, if one leg of the calendar spread is expiring that day, the margin offset will not be available. In effect, traders will have to maintain higher margins during market hours itself, instead of facing the margin spike only after the market closes when one leg ceases to exist.

SEBI’s reasoning is operational and risk-focused. Brokers reported that under the current system, clients maintain hedged positions at low margins until 3:30 PM. Once the market closes and the expiring leg lapses, the remaining open position becomes unhedged and attracts sharply higher margin requirements. Since markets are already shut, brokers can only ask clients to post additional margins after the fact, exposing trading members to overnight risk if clients fail to comply or markets move adversely.

The regulator noted that this structural gap left brokers with limited recourse in case of margin shortfalls and price shocks. By removing the benefit during market hours, SEBI is effectively forcing margin alignment before the risk materialises, rather than after.

The rule also aligns the treatment of single stock derivatives with index derivatives, where similar margin benefits are not available on expiry day.

The mechanics of the change are precise. If three monthly expiries fall on the 29th, 30th, and 31st, calendar spreads involving the 29th and 30th or the 29th and 31st will not qualify for spread margins on the 29th. However, spreads involving only the 30th and 31st will continue to receive the benefit, since neither leg is expiring that day.

For retail and proprietary traders who rely heavily on calendar spreads for leverage-efficient positioning, this change raises the effective capital requirement on expiry sessions. For brokers and exchanges, it potentially alters intraday trading behaviour, especially on monthly expiry days which typically see peak derivatives volumes.

This is where the market impact becomes more nuanced.

A significant portion of derivatives turnover in India, particularly in stock futures and options, is driven by strategies that optimise margin usage. Calendar spreads are among the most popular because they allow traders to hold large notional positions with relatively small capital outlay. By increasing the margin requirement at a critical time window, SEBI may be indirectly dampening such activity.

That has implications for brokerage revenues, exchange transaction charges, and depository-linked settlement volumes. Stocks like Nuvama and BSE reacted not because of an immediate earnings hit, but due to concerns that expiry-day trading intensity-a key revenue driver-could moderate once this rule kicks in.