SEBI F&O Limits: Margin, Lot Size, STT Changes

SEBI circular that triggered the latest F&O debate

SEBI’s circular SEBI/HO/MRD/TPD/CIR/2026/034, effective 1 May 2026, is at the centre of current Reddit and social chatter on derivatives risk. Users describe it as the outcome of an 18-month regulatory push to curb speculative excess in F&O. The context being cited is a sharp rise in retail participation, with posts quoting an estimated 1.2 crore active traders by December 2025. The same discussions repeatedly reference SEBI research that 93% of individual F&O traders made net losses in FY24. Against that backdrop, the circular is being discussed as a move toward tighter margin discipline and closer monitoring of large positions. People are also focusing on changes that reduce implicit leverage, especially in index options. The debate is less about whether rules changed and more about how capital requirements shift for common retail strategies.

Retail position limits revised downward in stock derivatives

One of the most-cited changes is a downward revision in position limit caps for retail participants. Posts compare the older regime, where liquid stock contracts could allow position ceilings of about 10-15% of open interest, versus an updated 5-8% range based on liquidity classifications. Traders interpret this as a direct constraint on scaling positions in single-stock futures and options. Social media also highlights that market-wide position limits in single-stock derivatives are now more tightly linked to free float and actual cash-market delivery volumes. A frequently repeated formulation is MWPL being recalibrated to the lower of 15% of free float or 65 times average daily delivery value (ADDV), with a floor of 10% of free float. In parallel, open interest measurement is being discussed as moving to a Delta-adjusted Future Equivalent (FutEq) approach rather than simple notional counting. Another point circulating is that during F&O ban periods, fresh positions must result in a net reduction of delta-based open interest. The intended effect, as traders frame it, is to reduce the ability to build oversized exposure in relatively illiquid stocks.

Margin recalibration across F&O and the Nifty futures example

Margin requirements have been described online as “recalibrated across all F&O segments,” with index futures initial margins up by 200-300 basis points in the most shared summaries. Posters are also attributing contract-level differences to SEBI-NSE calibration models implemented through May 2026. The most repeated retail example is the step-up in margin capital needed for a single Nifty 50 futures position. In the shared figures, a position that earlier needed around Rs 1.5-2 lakh is now closer to Rs 2.2-2.5 lakh. For traders who run multiple lots or maintain hedges, that increase is being treated as a meaningful change in deployed capital. Separate threads focus on the impact on intraday activity, where higher margins reduce the number of positions a trader can carry simultaneously. Some also connect the margin shift to stricter enforcement, with intraday monitoring of limits occurring multiple times a day through random snapshots rather than only end-of-day checks. Overall, the tone is that strategy viability now depends more heavily on margin planning than on just directional views.

Option buying: premium plus additional margin upfront

A major point of discussion is the new minimum margin for option buyers, described as premium plus 5% of the notional contract value. Traders are sharing a worked example for a Nifty 25,000 call option priced at Rs 200. Under the older approach, the margin was the premium paid, often illustrated as Rs 5,000 when multiplied by a 25 lot size. Under the updated rule shared online, margin becomes Rs 5,000 plus Rs 31,250 (5% of 25,000 x 25), totalling Rs 36,250. Many commenters interpret this as a 5-7 times jump in capital required for option buying, particularly for short-dated trades. Another frequently cited operational rule is that brokers must collect the full option premium upfront from buyers before executing trades. People also mention that brokers must collect margins upfront for intraday option positions, addressing the practice where some platforms effectively allowed leverage until peak margin checks. Taken together, these changes are being framed as reducing low-capital speculative turnover in index options.

Expiry-day risk controls and the rise in extreme loss margins

Expiry-day margin behaviour is another focus, especially for short option sellers who depend on stable spread benefits and predictable ELM. One widely circulated line is that an additional Extreme Loss Margin (ELM) is imposed on short options contracts on expiry day, applying to open short positions at the start of day as well as new short positions initiated that expire the same day. However, social posts are not fully consistent on the exact number, with some citing an additional 2% ELM and others citing 12% ELM on expiry day. The higher number is often paired with a concrete example: a short Nifty straddle on expiry day requiring roughly Rs 8-9 lakh margin versus Rs 4-5 lakh previously. Traders also point out that margin benefits for calendar spreads no longer apply on the day of expiry, which can change the economics of rolling or hedging. Separately, penalties for margin shortfalls are being reshared as a daily levy that escalates with the shortfall amount. The discussion is that expiry day now has tighter guardrails for both leverage and operational risk.

Bigger contract sizes and lot size adjustments lift entry capital

Another high-impact update being discussed is the mandated increase in minimum contract value for index derivatives to about Rs 15 lakh, from an earlier Rs 5-10 lakh band. Exchanges are required to keep contract values within roughly Rs 15-20 lakh by adjusting lot sizes. For retail traders, this is being framed as a structural reduction in how many lots can be traded with the same capital base. Posts also note that for individual stock options, lot sizes have been revised to ensure minimum contract values of about Rs 7.5 lakh, up from roughly Rs 2-4 lakh earlier. In some threads, users describe this as effectively tripling the minimum capital needed to trade a single lot of index options. For Nifty 50 specifically, one table being shared shows the lot size moving from 25 to 75 with an approximate contract value of Rs 16.5 lakh, with another note that it has since moved to 65 based on index levels. Bank Nifty and FinNifty lot size adjustments are also being circulated in the same framing - keeping the notional contract value in the new range. The practical takeaway in discussions is that position sizing becomes coarser and risk per lot becomes more meaningful.

Weekly expiry restrictions reshape index options activity

Reddit threads repeatedly highlight the weekly expiry restriction as a major market-structure change. Under the shared interpretation, each exchange can offer only one weekly expiry per index. NSE is said to retain weekly options only for Nifty (Thursday) and convert Bank Nifty and Fin Nifty to monthly-only expiries. BSE is said to retain Sensex weekly options (Friday). Traders expect this to concentrate weekly volumes into fewer products and reduce the menu of short-dated trading opportunities. Some users also link this to lower “expiry day churn” across multiple indices in the same week. Others focus on how strategy calendars change, especially for those who traded Bank Nifty weekly options as a primary instrument. Because many retail strategies are built around frequent expiries, the restriction is being treated as a behavioural lever, not just a contract design choice. The operational effect discussed is that hedging and rolling mechanics shift toward monthly cycles for certain indices.

STT hikes and why costs matter more when margins rise

Transaction costs are being re-examined in the same conversation because margins and lot sizes are increasing at the same time. Posts claim STT on futures has increased from 0.02% to 0.05%. Options premiums are also said to attract 0.15% STT, up from 0.1%. Traders are explicitly describing this as a 150% increase in futures taxation and a 50% increase in options taxation, based on those rates. The combined effect, as discussed, is that break-even thresholds rise for short-horizon trades, especially those that rely on small point gains. For many retail participants, higher STT plus higher margins changes return-on-capital calculations even when a strategy’s gross profitability stays the same. Some users also connect higher costs to the push toward fewer, better-planned trades rather than high-frequency churn. Cost sensitivity is also being discussed in relation to squaring-off rules and penalties, because forced exits can lock in slippage and costs.

Compliance timeline, reporting, and what traders are doing next

The rollout is being discussed as a three-phase compliance framework with dated operational milestones. Phase 1 is described as immediate, requiring brokers to notify existing clients of position limit changes with a 10-day adjustment window. Phase 2 is described as starting 1 June 2026, with automatic position blocking at revised limit thresholds and broker implementation of automated margin calculation engines by 31 May 2026. Phase 3 is described as effective 1 July 2026, eliminating grandfathering provisions and enabling automatic squaring-off for positions above revised limits after a 48-hour prior notice. Another widely shared point is that existing positions established before the regulatory announcement had transition protections through 30 June 2026, after which full compliance becomes mandatory. Separately, social posts highlight big-trader reporting, where aggregate F&O positions exceeding Rs 50 crore notional across exchanges require registration and daily position reporting. There is also discussion of stricter real-time monitoring of position limits for equity index derivatives. Across threads, the most practical takeaway is that traders are reassessing position sizing, margin buffers, and expiry-day exposure to avoid forced reductions or penalties.