SEBI Opens Consultation on Closing Auction Session and Derivatives Settlement Methodology
The Securities and Exchange Board of India (SEBI) has opened a consultation on proposed changes to the Closing Auction Session (CAS) and the methodology used for settling derivatives contracts.
The move comes after the initial experience with the CAS mechanism, which was introduced for eligible stocks from August 3, 2026.
SEBI is now seeking market feedback on issues including expiry-day derivatives settlement prices, market timings, the interaction between continuous trading and CAS, Indicative Equilibrium Price (IEP), order types and information dissemination.
For F&O traders, the consultation is important because the closing price of the underlying security can have a significant impact on the final settlement value of derivatives, particularly on expiry days.
Why SEBI Is Reviewing the CAS Framework
Before the introduction of CAS, the closing price of eligible stocks was generally determined using the Volume Weighted Average Price (VWAP) of trades executed during the final 30 minutes of the Continuous Trading Session (CTS).
Under the new CAS framework, closing prices are determined through an auction-based price discovery mechanism, using aggregate buy and sell orders.
While the mechanism was intended to improve closing-price discovery, market participants have raised concerns about its interaction with derivatives trading around expiry.
SEBI is therefore examining whether the existing methodology should be modified.
Two Options Proposed for Derivatives Settlement
One of the most important parts of the consultation concerns the methodology for calculating settlement prices for index and single-stock derivatives on expiry days.
SEBI is considering two alternatives.
Option 1: Blended VWAP
Under the first approach, the settlement price would use a combination of the Continuous Trading Session VWAP and the Closing Auction Session price/VWAP.
This approach attempts to combine the broader trading activity during the continuous session with the price discovered during the closing auction.
The objective is to reduce the possibility that a relatively concentrated auction at the close could have a disproportionate impact on derivatives settlement.
Option 2: CTS VWAP
The second approach would retain the Continuous Trading Session VWAP as the basis for derivatives settlement.
This would keep the settlement methodology closer to the system that existed before the CAS mechanism was introduced.
SEBI is seeking stakeholder views on both alternatives before deciding the final framework.
Why the Settlement Price Matters to F&O Traders
The settlement price is particularly important on expiry days.
A relatively small movement in the underlying stock or index near the end of the trading session can significantly affect the value of futures and options.
This becomes even more important for traders holding positions close to expiry, particularly option sellers and traders with large gamma exposure.
A change in the methodology could therefore affect the way traders manage positions during the final part of expiry sessions.
SEBI Looking at Market Timings
SEBI is also considering changes to the timing of the various market sessions.
One proposal would retain the CAS after 3:30 PM, while another option would keep CAS beginning after 3:15 PM.
The regulator is also considering reducing the transition period between continuous trading and CAS from the current arrangement to approximately one minute.
These changes are intended to make the transition between the different trading phases more efficient.
F&O Trading Window Could Be Shortened
Another proposal concerns the derivatives trading period after the CAS.
SEBI is considering reducing the post-CAS derivatives trading window to around five minutes.
This would alter the amount of time available to F&O traders after the underlying securities have completed the closing-auction process.
For traders, the change could make the final minutes of expiry sessions even more important.
What Happens to the CAS Price Band?
SEBI is also examining operational aspects of the CAS mechanism.
The existing ±3% price band is being considered as part of the review, while the broader consultation also looks at how the auction price and related information are displayed.
The regulator is seeking feedback on whether changes are required to make the price-discovery process more efficient and transparent.
IEP and Final Closing Price
Another important issue being examined is the distinction between the Indicative Equilibrium Price (IEP) and the final closing price.
The IEP reflects the price that could emerge based on the orders available during the auction.
However, it is not the same as a final executed market price.
SEBI is therefore examining how information relating to the IEP, final closing price and derivatives settlement price should be presented to market participants.
Indicative Index Value Also Under Review
SEBI is also examining the role of the Indicative Index Value (IIV) during the CAS period.
The consultation considers whether the display of index-level indicative values during CAS should be changed, while continuing to provide relevant price information for individual securities.
This is important because derivatives traders use index values to assess the potential impact on their positions during expiry.
Iceberg Orders Could Be Allowed During CAS
The regulator is also considering changes to the types of orders permitted during the Closing Auction Session.
One proposal involves allowing iceberg orders during CAS.
Iceberg orders allow a participant to display only part of a larger order at a time, potentially helping large participants manage execution without displaying the entire order size to the market.
Why This Matters for Nifty and Bank Nifty Traders
For traders in Nifty, Bank Nifty and stock derivatives, the most important issue is the final settlement methodology.
If the settlement price moves away from the method currently linked to CAS, expiry-day trading strategies may need to be adjusted.
The change could affect:
- Options settlement
- Futures settlement
- Expiry-day volatility
- Option premiums near expiry
- Hedging strategies
- Market-making activity
- Arbitrage strategies
- Large option positions
- Risk-management systems used by brokers
However, these are proposed changes, not final regulations.
Could This Reduce Expiry-Day Volatility?
One of the broader objectives of the proposed changes is to improve the interaction between cash-market price discovery and derivatives settlement.
The introduction of CAS created a new relationship between the closing auction price and expiry settlement.
SEBI’s consultation suggests that the regulator is now examining whether the current structure provides the most appropriate outcome for derivatives markets.
The final impact will depend on which settlement methodology is eventually adopted.
What Investors and Traders Should Watch
Market participants should focus on four key developments:
1. Final Settlement Methodology
The decision between a blended methodology and CTS-based VWAP could have the biggest direct impact on expiry trading.
2. CAS Timing
Any change to the starting time or transition period could alter trading behaviour near the close.
3. Derivatives Trading Window
A shorter post-CAS F&O window could change the way traders manage positions during expiry.
4. Final SEBI Circular
The consultation paper is not the final rule. The existing framework remains applicable until SEBI announces and implements any changes.
SEBI Seeks Public Comments
SEBI has invited comments from market participants and other stakeholders on the proposed changes.
According to reports on the consultation, the feedback window is open until October 3, 2026.
The regulator will consider the feedback before deciding on the final framework.
Investor and Trader Takeaway
SEBI’s consultation is an important development for India’s derivatives market.
The regulator is not simply abandoning the Closing Auction Session. Instead, it is reviewing how CAS interacts with derivatives settlement, expiry-day trading and price discovery.
For F&O traders, the most important proposal is the possible change in the expiry-day settlement methodology, with a blended VWAP approach and CTS VWAP approach being considered.
Until SEBI issues a final decision, traders should continue to follow the existing rules rather than position themselves based on the proposed changes.
The consultation nevertheless signals that India’s closing-price and derivatives settlement framework is entering a new phase of calibration after the initial CAS rollout.
Key Points
- CAS introduced: August 3, 2026
- Regulator: SEBI
- Key issue: Derivatives settlement methodology
- Settlement options: Blended VWAP and CTS VWAP
- CAS timing: Under review
- Transition period: Proposed reduction
- Post-CAS F&O window: Proposed five minutes
- CAS price band: ±3% currently
- Iceberg orders: Proposed for CAS
- Public comments: Invited
- Current status: Consultation/proposal, not final rules
Official Source
SEBI Consultation Paper:
SEBI – Consultation on Closing Auction Session and Derivatives Settlement Methodology
SEBI website:
Securities and Exchange Board of India (SEBI)
Additional reporting: The Economic Times has also reported on the proposed CAS and derivatives-settlement changes.
Disclaimer
This article discusses SEBI’s consultation proposals and does not represent final regulatory changes. The existing trading and settlement framework will continue to apply until SEBI issues final directions. Traders and investors should refer to official SEBI and exchange circulars before making trading or investment decisions.