India F&O FY26 rule changes: losses fall, CAS begins

India’s equity derivatives market has been at the centre of a long, noisy debate on Reddit and trading communities, largely because the rulebook kept changing between late 2024 and August 2026. The discussion now blends two threads: whether the changes reduced retail damage in FY26, and how the new Closing Auction Session (CAS) alters end-of-day price discovery for F&O-eligible stocks.

Why India F&O rules became a hot topic again

The current debate follows a series of regulatory steps implemented between late 2024 and August 2026. The stated aim behind these measures was to curb excessive speculation and tighten risk management in equity derivatives. Over time, the changes touched contract sizes, margins, expiry structures, and the cost of trading via higher taxes. Social media chatter intensified because many of these moves directly affect how small traders place weekly option bets. The sequence also matters because SEBI introduced several measures in phases, rather than through one large overhaul. The latest change in August 2026 is structural, because it changes how closing prices for F&O-eligible stocks are discovered. That matters for traders who track closing levels for settlement, marking positions, and strategy exits. It also matters for those who previously tried to influence closing prints through concentrated activity near the close.

Timeline: phased tightening from Nov 2024 to Apr 2025

SEBI’s stricter risk-management measures were introduced in phases between November 2024 and April 2025. A key part of the framework was raising minimum contract sizes, which has been discussed online as moving typical notional values to about ₹15–20 lakh. SEBI also introduced tighter margin practices, including a 50:50 cash margin requirement that traders frequently cite as reducing leverage flexibility. Another repeated theme was reduced choice in weekly expiries and rationalisation of weekly index derivatives products. The regulator also raised risk cover on expiry days by increasing tail-risk coverage. Short option positions on expiry days faced additional Extreme Loss Margin (ELM) requirements, which traders often interpret as making expiry-day selling more expensive. Separately, SEBI required upfront collection of option premium from buyers, shifting cash-flow expectations for option purchasers. It also brought in intraday monitoring of position limits to strengthen day-to-day supervision.

Expiry structure changes: fewer weekly expiries to trade

One of the most visible changes for active traders was the reduction in weekly expiry choices. SEBI limited weekly derivative contracts to one index per exchange, a move repeatedly referenced in FY26 discussions. This was paired with rationalisation of weekly index derivatives products and rationalisation of monthly index derivative products. The debate on forums often focuses on how weekly options previously concentrated activity and encouraged frequent, smaller punts. With fewer weekly expiries, traders must adapt strategies that relied on multiple weekly contracts across indices. The shift also affects how traders manage rolling positions, because the available expiry calendar is more constrained. In May 2025, SEBI introduced further measures aimed at streamlining expiry days across exchanges. That May 2025 step also referenced implementing appropriate risk metrics for position limits for better monitoring and disclosure of risks in F&O. Together, these changes re-shaped how weekly and monthly derivatives are used, particularly for retail traders.

Margins and risk cover: upfront premiums and expiry-day ELM

Another cluster of measures focused on making risk explicit and collectible in real time. Upfront collection of option premium from buyers is a simple operational change but a meaningful one for capital planning. SEBI also removed certain margin benefits around expiry, and removed calendar spread treatment on the expiry day as per the Finance Ministry’s listing of measures. Traders flagged that this can increase required funds when positions are carried into expiry sessions. Increased tail-risk coverage on the day of options expiry and higher expiry-day risk cover were designed to address sharp intraday moves. Additional ELM requirements on short option positions on expiry days were also part of the tightening. Intraday monitoring of position limits was introduced to keep tabs on exposures while markets are open. These steps collectively changed the cost and feasibility of high-frequency expiry trading for many participants. Online debate tends to split between those who see it as necessary risk control and those who see it as an access barrier.

STT and trading costs: what changed after Oct 1, 2024

Costs rose not only through margins but also through taxes. The Centre raised the Securities Transaction Tax (STT) on equity derivatives effective 1 October 2024, and this became a recurring point in trader discussions. In FY26, STT collected from F&O trades across NSE and BSE was reported at ₹27,695 crore, up sharply from ₹6,634 crore in FY22. The FY26 split shared in the same discussion indicates options accounted for ₹19,802 crore, while futures contributed ₹7,893 crore. These figures are frequently cited to argue that even as some volumes cooled, tax collections remained substantial. Traders also interpret higher STT as a headwind for very short-term strategies where costs compound quickly. The STT change sits alongside other measures, so it is hard to isolate its impact in casual conversation. Still, the jump in collections became a headline statistic that fuels the wider debate on market structure. It also underlines how heavily options contribute to overall derivatives-related STT.

What Parliament data says: FY26 losses and participation

A Rajya Sabha reply cited in the discussion stated that regulatory measures curtailed aggregate net losses of retail investors in the equity derivatives segment to ₹91,685 crore in FY26, down from about ₹1.12 lakh crore in the preceding fiscal year. The same reply noted a year-on-year decline in the number of unique individual investors from 98.1 lakh to 78.6 lakh. Separately, equity derivatives turnover was reported to have dropped to ₹202 lakh crore in FY26 from ₹213 lakh crore in FY25. The Finance Ministry also noted that per-investor loss increased a bit even as aggregate losses fell, a nuance frequently debated online. For some traders, this suggests that lighter participation did not automatically mean lower losses for those who remained active. For others, the lower aggregate loss number is seen as evidence that the overall retail harm reduced. The reported decline in unique individuals is often read as a sign that tighter rules reduced casual participation. Taken together, these data points frame the FY26 conversation more than anecdotal profit and loss screenshots.

August 3, 2026 CAS: new closing price discovery for F&O stocks

The most recent structural update is SEBI’s Closing Auction Session (CAS) for F&O-eligible stocks, implemented from August 3, 2026. This change replaced the earlier 30-minute VWAP-based closing mechanism used to determine closing prices for eligible stocks. Under CAS, the official closing price is determined through an auction-based price-discovery process. The timeline around the close also changes: trading in F&O-eligible stocks ends at 3:15 PM, followed by the closing auction. At the same time, index and stock F&O contracts continue to trade until 3:40 PM, as stated in the context. Traders discuss CAS because closing prices feed into portfolio marking and settlement references in many workflows. VWAP-based methods were often criticised online for being sensitive to concentrated end-of-day prints. An auction-based mechanism is seen as a different approach to concentrate liquidity for price discovery, though the debate is now about how it behaves in volatile sessions. The operational detail about separate end times is also relevant for those managing hedges between cash and derivatives.

What traders are watching next under the FY26 framework

The FY26 framework now commonly referenced online includes higher contract sizes of about ₹15–20 lakh notional value, limits on weekly expiries for each index, and mandatory upfront collection of option premiums. It also includes expiry-day risk cover measures and intraday monitoring of position limits, which affect day traders and positional traders differently. With CAS live for F&O-eligible stocks, closing prints will likely get more attention, especially from traders who benchmark strategies to the official close. Discussions also focus on whether reduced participation is a temporary adjustment or a lasting shift. The FY26 data cited publicly shows lower aggregate losses and fewer unique individuals, but also mentions a slight rise in average loss per trader. That mix keeps the debate open-ended, because different people interpret the same figures differently. For retail participants, the practical takeaway is that capital requirements and closing mechanics have changed materially since late 2024. For the broader market, the measures represent a sustained attempt to tighten risk controls in one of India’s most active segments.