SEBI Revises CAS & Settlement Rules 2026

SEBI Revises CAS & Settlement Rules 2026. The Securities and Exchange Board of India has revised the Closing Auction Session, market timings and the method used to determine settlement prices for expiring derivatives contracts. These changes are relevant to investors, traders, stock brokers, clearing members and other securities market participants.
The revised addresses several connected areas, including the timing of the closing auction, permitted order types, the treatment of pending orders and the calculation of derivatives expiry settlement prices. Understanding these distinctions is important because the official closing price of a security and the settlement price of a derivatives contract do not necessarily serve the same purpose. SEBI issued the circular on 15 October 2026. Most changes will take effect on 7 December 2026, while the revised provisions concerning the carry-forward of unexecuted orders will take effect on 8 February 2027.
What Is the Closing Auction Session?
Meaning and Purpose of CAS
The Closing Auction Session, commonly called CAS, is a separate auction process for determining the closing price of applicable securities in the equity cash market. During the session, buying and selling interest is collected and matched according to the prescribed auction rules.
The closing price is an important market reference. Investors use it to review portfolio values, institutions may use it when evaluating execution, and market participants refer to it when comparing daily price movements. A structured auction provides a specific process through which this price is established.
Difference Between CAS and Continuous Trading
During the Continuous Trading Session, or CTS, compatible buy and sell orders can match throughout the trading period. Prices change as transactions occur and new information enters the market. CAS works differently. Orders are collected during defined stages before matching takes place.
An order entered into the auction should therefore not be assumed to execute immediately in the same way as an executable order placed during continuous trading. This difference affects execution planning. Participants need to understand the session in which they are placing an order, the type of order permitted and the conditions governing its treatment.
Why Has SEBI Revised the CAS Structure?
Reviewing the Operation of the Earlier Structure
The earlier CAS was introduced to support transparent and efficient discovery of closing prices. Following implementation, SEBI reviewed its functioning and its interaction with derivatives settlement. A closing auction can influence several connected activities. These include the execution of cash-market orders, the valuation of positions and the assumptions used in expiry-day strategies. Reviewing these relationships helps identify where operational changes may be needed.
Incorporating Consultation and Market Feedback
The revision followed a consultation process, recommendations from SEBI’s Secondary Market Advisory Committee and discussions with stock exchanges. The changes demonstrate the importance of assessing how a operates in practice. A market procedure must be understood not only as a regulatory rule but also through its effects on order handling, system controls and participant behaviour.
Revised Closing Auction Session Timings

Reference Price Calculation and Transition: The revised CAS begins at 3:30 p.m. The first minute, from 3:30 p.m. to 3:31 p.m., is allocated to reference price calculation and the transition from continuous trading to the auction. This stage establishes the operational starting point for CAS. Participants should distinguish it from the subsequent order-entry stages rather than treating the entire auction window as one uninterrupted period with identical permissions.

Entry of Limit and Market Orders: From 3:31 p.m. to 3:36 p.m., both limit orders and market orders may be entered. A limit order specifies a price condition, while a market order does not specify a limit price. Their treatment during the auction remains subject to the applicable matching rules and available buying and selling interest. Neither order type should be understood as guaranteeing execution in every circumstance.

Final Order-Entry Stage and Random Closure: From 3:36 p.m., new order entry is restricted to limit orders. Market orders cannot be modified or cancelled during this stage. The order-entry session closes randomly between 3:38 p.m. and 3:40 p.m., through a system-driven process. Participants should therefore avoid assuming that they can always submit or change instructions until exactly 3:40 p.m. After order entry closes, the exchange undertakes matching under the CAS and disseminates the closing price and executed quantity.

Revised Trading Timings for Derivatives

Index Derivatives: Trading in index derivatives will continue until 3:45 p.m. on trading days. However, expiring index derivatives contracts will stop trading at 3:30 p.m. on their expiry day. The distinction concerns the expiring contracts. Participants should not assume that every index derivatives contract stops trading at 3:30 p.m. merely because an expiry occurs that day. For example, a trader holding positions across different expiries must identify the applicable cut-off for each contract rather than relying on a single segment-wide assumption.

Stock Derivatives: Trading in stock derivatives will continue until 3:45 p.m. on all trading days, including expiry days. This creates an important difference between expiring index derivatives and stock derivatives. Brokers, dealers and trading systems should correctly identify the instrument before applying trading controls or communicating deadlines to clients.

Cash-Market Post-Close Session: The cash-market post-close session will operate from 3:50 p.m. to 4:00 p.m., with trades executed at the closing price of the securities. This session is separate from continuous trading and the closing auction. Participants should understand the purpose of each session and avoid interpreting the post-close window as an extension of ordinary price discovery.

How Will the CAS Reference Price Be Calculated?
Last 15-Minute VWAP
The CAS reference price will be based on the Volume Weighted Average Price of trades during the final 15 minutes of continuous trading in the relevant security. VWAP accounts for both transaction prices and traded quantities. Transactions involving larger quantities carry greater weight in the calculation than transactions involving smaller quantities.
For illustration, if 100 shares trade at Rs.100 and 300 shares trade at Rs.102, their combined VWAP is Rs.101.50. This differs from a simple average of Rs.101 because the larger transaction receives more weight.
Fallback Where Trading Is Absent
If no trade occurs in the security during the final 15 minutes of CTS, its last traded price during the day becomes the reference price. If the security does not trade throughout the day, the previous trading day’s closing price is used. Where a corporate action applies, the relevant adjusted closing price or base price is considered under the structure. These alternatives provide a reference when the preferred trading data is unavailable.
Revised Settlement Method for Expiring Derivatives
Settlement of Index Derivatives
On expiry day, the settlement price of expiring index derivatives will be based on the underlying index value calculated using the VWAPs of its constituent securities during the last 30 minutes of CTS in the equity cash market. This is different from simply taking the last displayed index value or assuming that the auction closing value determines expiry settlement. Traders should check the inputs used in their internal estimates. A model that relies on an unsuitable price proxy may produce an inaccurate expectation of the settlement outcome.
Settlement of Stock Derivatives
The settlement price of expiring stock derivatives will be determined by clearing corporations using the underlying stock’s VWAP during the last 30 minutes of CTS across stock exchanges. The calculation therefore concerns the underlying cash-market security. It should not be confused with the last traded price of the derivatives contract itself.
Dissemination of Indicative Values
The requires exchanges to calculate and continuously disseminate the relevant indicative index values or stock VWAP information during the final 30 minutes of CTS. This information can help participants follow the developing calculation. However, an indicative figure remains provisional and should not be presented as the final settlement result before the calculation is complete.
Why Closing Price and Settlement Price Must Be Distinguished

Different Functions of the Two Prices: The CAS closing price is established through the auction mechanism for applicable securities. The derivatives expiry settlement price is calculated under the prescribed settlement methodology. Although both relate to end-of-day market activity, they perform different functions. Participants should identify which price is relevant before assessing a transaction, preparing a report or calculating an expected outcome.

Practical Example: Suppose a stock’s auction closing price differs from the VWAP calculated over the final 30 minutes of continuous trading. A participant who assumes the two figures must be identical could misunderstand the settlement calculation. The practical lesson is to label prices accurately. Trading screens, spreadsheets and reports should distinguish the auction closing price, indicative VWAP and final settlement price.

Treatment of Unexecuted Limit Orders
Carry-Forward into CAS
Under the revised carry-forward provisions, unexecuted limit orders pending at the end of CTS will generally transition into CAS. This means an order that remains unfilled during continuous trading may continue to participate in the auction. The trader’s original execution plan should account for this possibility.
Orders Excluded from Transition
Stop-loss orders and orders with prices outside the applicable CAS price bands will not be carried forward under these provisions. Participants should check the status of their orders rather than assume that all pending instructions receive identical treatment. Brokers should also explain relevant order behaviour clearly through their platforms and client communications.
Treatment of Unexecuted Iceberg Orders
Transition as Fully Disclosed Limit Orders
Eligible unexecuted iceberg orders within the applicable CAS price bands will transition as fully disclosed limit orders unless the participant opts out when placing the original order. This matters because an iceberg order is generally designed to reveal only part of a larger quantity. Transition into a fully disclosed order changes the visibility of the remaining quantity. Participants should therefore understand the available transition choice before submitting the original order.
Time Priority and Modification
Transitioned iceberg orders receive lower time priority than other limit orders carried forward from CTS. Among the transitioned iceberg orders, priority is determined by reference to their original order time. Carried-forward limit and iceberg orders have higher time priority than limit orders newly entered during CAS. They may be modified, but modification changes their time priority. These rules make order history relevant. Two orders at the same price may have different execution priority because of their origin or subsequent modification.
Other Operational Changes

Stock Futures Price Bands: During 3:30 p.m. to 3:45 p.m., stock futures price bands will align with the price bands applicable during CAS. The existing dynamic price-band flexing will not apply during that period. Trading and risk systems should therefore recognise that the treatment of price bands can depend on the stage of the trading day.

Order-Level Margin Requirements: CAS orders are subject to applicable order-level margin requirements, with specified treatment for orders carried forward from CTS. If carried-forward orders are modified during CAS, applicable order-level margin requirements apply to them. Participants should not assess modification solely as a price or quantity decision. Its implications for priority and margin treatment also need attention.

Special Trading Sessions: For special trading sessions, CAS retains the prescribed duration. The also provides a sequence for the close of derivatives trading and the subsequent post-close session. Participants should follow the exchange schedule announced for the particular special session rather than assume ordinary clock timings apply.

Implementation Dates

Changes Effective from 7 December 2026: Most modifications, including the revised timings and derivatives settlement methodology, take effect from 7 December 2026. Businesses should use the preparation period to review systems, procedures, staff instructions and client communications. The announcement date should not be confused with the implementation date.

Changes Effective from 8 February 2027: The revised provisions concerning unexecuted limit and iceberg order transitions take effect from 8 February 2027. Maintaining separate implementation records for the two dates can help prevent a partial update from being treated as full compliance with the revised.

Practical Implications for Traders and Investors

Review Execution Assumptions: Traders should review strategies that depend on trading until a particular time, using a particular closing-price proxy or carrying orders into the auction. A useful exercise is to trace one planned transaction through order placement, session transition, execution and settlement. This can reveal assumptions that need to be corrected.

Check Broker Communications: Investors should read their broker’s implementation notices and platform instructions. These may explain how the revised affects available order choices, internal processing and displayed information. Understanding these details before placing an order can reduce avoidable disputes over rejected instructions or unexpected order treatment.

Maintain Appropriate Risk Controls: The changes do not guarantee profits or eliminate market risk. Derivatives remain capable of producing substantial losses, and execution may differ from expectations. Participants should reassess their assumptions while maintaining controls appropriate to their positions, liquidity requirements and capacity to bear losses.

Preparation for Brokers and Compliance Teams

System Testing: Brokers can test session transitions, instrument-specific cut-offs, order carry-forward settings and reporting. Testing should include rejected instructions and interruptions as well as successful transactions. Client-facing messages should clearly explain what happened when an instruction cannot proceed.

Staff Training and Documentation: Dealers, operations teams and support staff should understand the distinction between reference prices, closing prices and settlement prices. Internal procedures should identify responsibilities and implementation dates. Scenario-based training can help staff explain the in practical language.

Reconciliation and Reporting: Businesses should check consistency between trading screens, back-office records and client reports. Where different prices legitimately appear, their descriptions should make the reason understandable. A sample transaction review can help confirm that records remain consistent from order entry through settlement reporting.

Conclusion
SEBI’s revised CAS changes the organisation of closing-session trading, pending-order treatment and derivatives expiry settlement. Its practical significance lies in understanding the correct session, instrument, price and implementation date for each activity.
Investors and traders should review execution assumptions and broker instructions. Intermediaries should coordinate technology, operations, risk and client support before the changes take effect. Careful preparation can help reduce operational errors and improve understanding of the revised market.
Need Help with SEBI Registration or Securities Market Compliance?
Planning to establish an investment advisory or research analyst business in India? Compliance Calendar LLP can help you understand the requirements for SEBI Investment Adviser Registration, Research Analyst Registration and applicable securities market compliances. Our team can guide you through the registration process, assist with documentation and help you understand regulatory updates relevant to your business.
Get in touch with Compliance Calendar LLP today!

Call/WhatsApp: +91 9988424211

Email: info@ccoffice.in

Frequently Asked Questions (FAQ’s)
Q1. What does CAS mean?
Ans. CAS stands for Closing Auction Session. It is an auction process used to determine the closing prices of applicable securities.
Q2. When will the revised structure take effect?
Ans. Most changes take effect on 7 December 2026. The revised unexecuted-order carry-forward provisions take effect on 8 February 2027.
Q3. What are the revised CAS timings?
Ans. CAS runs from 3:30 p.m. to 3:40 p.m., with separate transition and order-entry stages. Order entry closes randomly between 3:38 p.m. and 3:40 p.m.
Q4. Do all derivatives contracts stop trading at 3:30 p.m. on expiry days?
Ans. No. The 3:30 p.m. cut-off applies to expiring index derivatives. Stock derivatives continue until 3:45 p.m., including on expiry days.
Q5. Is the CAS reference price the same as the expiry settlement price?
Ans. No. The CAS reference generally uses the final 15-minute CTS VWAP, while the revised expiry settlement methodology uses relevant final 30-minute CTS VWAP inputs.
Q6. Will the changes remove trading risk?
Ans. No. Revised trading and settlement procedures do not guarantee returns or protect participants from market losses.
Q7. Can market orders be modified or cancelled during the final CAS stage?
Ans. No. From 3:36 p.m. until random closure, market orders cannot be modified or cancelled. Only new limit orders may be entered during this stage.
Q8. Will unexecuted iceberg orders move into CAS?
Ans. Eligible iceberg orders will transition as fully disclosed limit orders unless the participant opts out when placing the original order. This provision takes effect on 8 February 2027.
Q9. How is the CAS reference price determined when no trades occur?
Ans. If no trades occur during the final 15 minutes of continuous trading, the day’s last traded price is used. If there are no trades throughout the day, the previous closing price applies, with adjustments where relevant for corporate actions.
Q10. What are the revised cash-market post-close session timings?
Ans. The post-close session will run from 3:50 p.m. to 4:00 p.m., with trades executed at the securities’ closing prices, effective 7 December 2026.

The Securities and Exchange Board of India has revised the Closing Auction Session, market timings and the method used to determine settlement prices for expiring derivatives contracts. These changes are relevant to investors, traders, stock brokers, clearing members and other securities market participants.

The revised addresses several connected areas, including the timing of the closing auction, permitted order types, the treatment of pending orders and the calculation of derivatives expiry settlement prices. Understanding these distinctions is important because the official closing price of a security and the settlement price of a derivatives contract do not necessarily serve the same purpose. SEBI issued the circular on 15 October 2026. Most changes will take effect on 7 December 2026, while the revised provisions concerning the carry-forward of unexecuted orders will take effect on 8 February 2027.

What Is the Closing Auction Session?

Meaning and Purpose of CAS

The Closing Auction Session, commonly called CAS, is a separate auction process for determining the closing price of applicable securities in the equity cash market. During the session, buying and selling interest is collected and matched according to the prescribed auction rules.

The closing price is an important market reference. Investors use it to review portfolio values, institutions may use it when evaluating execution, and market participants refer to it when comparing daily price movements. A structured auction provides a specific process through which this price is established.

Difference Between CAS and Continuous Trading

During the Continuous Trading Session, or CTS, compatible buy and sell orders can match throughout the trading period. Prices change as transactions occur and new information enters the market. CAS works differently. Orders are collected during defined stages before matching takes place.

An order entered into the auction should therefore not be assumed to execute immediately in the same way as an executable order placed during continuous trading. This difference affects execution planning. Participants need to understand the session in which they are placing an order, the type of order permitted and the conditions governing its treatment.

Why Has SEBI Revised the CAS Structure?

Reviewing the Operation of the Earlier Structure

The earlier CAS was introduced to support transparent and efficient discovery of closing prices. Following implementation, SEBI reviewed its functioning and its interaction with derivatives settlement. A closing auction can influence several connected activities. These include the execution of cash-market orders, the valuation of positions and the assumptions used in expiry-day strategies. Reviewing these relationships helps identify where operational changes may be needed.

Incorporating Consultation and Market Feedback

The revision followed a consultation process, recommendations from SEBI’s Secondary Market Advisory Committee and discussions with stock exchanges. The changes demonstrate the importance of assessing how a operates in practice. A market procedure must be understood not only as a regulatory rule but also through its effects on order handling, system controls and participant behaviour.

Revised Closing Auction Session Timings

Reference Price Calculation and Transition: The revised CAS begins at 3:30 p.m. The first minute, from 3:30 p.m. to 3:31 p.m., is allocated to reference price calculation and the transition from continuous trading to the auction. This stage establishes the operational starting point for CAS. Participants should distinguish it from the subsequent order-entry stages rather than treating the entire auction window as one uninterrupted period with identical permissions.
Entry of Limit and Market Orders: From 3:31 p.m. to 3:36 p.m., both limit orders and market orders may be entered. A limit order specifies a price condition, while a market order does not specify a limit price. Their treatment during the auction remains subject to the applicable matching rules and available buying and selling interest. Neither order type should be understood as guaranteeing execution in every circumstance.
Final Order-Entry Stage and Random Closure: From 3:36 p.m., new order entry is restricted to limit orders. Market orders cannot be modified or cancelled during this stage. The order-entry session closes randomly between 3:38 p.m. and 3:40 p.m., through a system-driven process. Participants should therefore avoid assuming that they can always submit or change instructions until exactly 3:40 p.m. After order entry closes, the exchange undertakes matching under the CAS and disseminates the closing price and executed quantity.

Revised Trading Timings for Derivatives

Index Derivatives: Trading in index derivatives will continue until 3:45 p.m. on trading days. However, expiring index derivatives contracts will stop trading at 3:30 p.m. on their expiry day. The distinction concerns the expiring contracts. Participants should not assume that every index derivatives contract stops trading at 3:30 p.m. merely because an expiry occurs that day. For example, a trader holding positions across different expiries must identify the applicable cut-off for each contract rather than relying on a single segment-wide assumption.
Stock Derivatives: Trading in stock derivatives will continue until 3:45 p.m. on all trading days, including expiry days. This creates an important difference between expiring index derivatives and stock derivatives. Brokers, dealers and trading systems should correctly identify the instrument before applying trading controls or communicating deadlines to clients.
Cash-Market Post-Close Session: The cash-market post-close session will operate from 3:50 p.m. to 4:00 p.m., with trades executed at the closing price of the securities. This session is separate from continuous trading and the closing auction. Participants should understand the purpose of each session and avoid interpreting the post-close window as an extension of ordinary price discovery.

How Will the CAS Reference Price Be Calculated?

Last 15-Minute VWAP

The CAS reference price will be based on the Volume Weighted Average Price of trades during the final 15 minutes of continuous trading in the relevant security. VWAP accounts for both transaction prices and traded quantities. Transactions involving larger quantities carry greater weight in the calculation than transactions involving smaller quantities.

For illustration, if 100 shares trade at Rs.100 and 300 shares trade at Rs.102, their combined VWAP is Rs.101.50. This differs from a simple average of Rs.101 because the larger transaction receives more weight.

Fallback Where Trading Is Absent

If no trade occurs in the security during the final 15 minutes of CTS, its last traded price during the day becomes the reference price. If the security does not trade throughout the day, the previous trading day’s closing price is used. Where a corporate action applies, the relevant adjusted closing price or base price is considered under the structure. These alternatives provide a reference when the preferred trading data is unavailable.

Revised Settlement Method for Expiring Derivatives

Settlement of Index Derivatives

On expiry day, the settlement price of expiring index derivatives will be based on the underlying index value calculated using the VWAPs of its constituent securities during the last 30 minutes of CTS in the equity cash market. This is different from simply taking the last displayed index value or assuming that the auction closing value determines expiry settlement. Traders should check the inputs used in their internal estimates. A model that relies on an unsuitable price proxy may produce an inaccurate expectation of the settlement outcome.

Settlement of Stock Derivatives

The settlement price of expiring stock derivatives will be determined by clearing corporations using the underlying stock’s VWAP during the last 30 minutes of CTS across stock exchanges. The calculation therefore concerns the underlying cash-market security. It should not be confused with the last traded price of the derivatives contract itself.

Dissemination of Indicative Values

The requires exchanges to calculate and continuously disseminate the relevant indicative index values or stock VWAP information during the final 30 minutes of CTS. This information can help participants follow the developing calculation. However, an indicative figure remains provisional and should not be presented as the final settlement result before the calculation is complete.

Why Closing Price and Settlement Price Must Be Distinguished

Different Functions of the Two Prices: The CAS closing price is established through the auction mechanism for applicable securities. The derivatives expiry settlement price is calculated under the prescribed settlement methodology. Although both relate to end-of-day market activity, they perform different functions. Participants should identify which price is relevant before assessing a transaction, preparing a report or calculating an expected outcome.
Practical Example: Suppose a stock’s auction closing price differs from the VWAP calculated over the final 30 minutes of continuous trading. A participant who assumes the two figures must be identical could misunderstand the settlement calculation. The practical lesson is to label prices accurately. Trading screens, spreadsheets and reports should distinguish the auction closing price, indicative VWAP and final settlement price.

Treatment of Unexecuted Limit Orders

Carry-Forward into CAS

Under the revised carry-forward provisions, unexecuted limit orders pending at the end of CTS will generally transition into CAS. This means an order that remains unfilled during continuous trading may continue to participate in the auction. The trader’s original execution plan should account for this possibility.

Orders Excluded from Transition

Stop-loss orders and orders with prices outside the applicable CAS price bands will not be carried forward under these provisions. Participants should check the status of their orders rather than assume that all pending instructions receive identical treatment. Brokers should also explain relevant order behaviour clearly through their platforms and client communications.

Treatment of Unexecuted Iceberg Orders

Transition as Fully Disclosed Limit Orders

Eligible unexecuted iceberg orders within the applicable CAS price bands will transition as fully disclosed limit orders unless the participant opts out when placing the original order. This matters because an iceberg order is generally designed to reveal only part of a larger quantity. Transition into a fully disclosed order changes the visibility of the remaining quantity. Participants should therefore understand the available transition choice before submitting the original order.

Time Priority and Modification

Transitioned iceberg orders receive lower time priority than other limit orders carried forward from CTS. Among the transitioned iceberg orders, priority is determined by reference to their original order time. Carried-forward limit and iceberg orders have higher time priority than limit orders newly entered during CAS. They may be modified, but modification changes their time priority. These rules make order history relevant. Two orders at the same price may have different execution priority because of their origin or subsequent modification.

Other Operational Changes

Stock Futures Price Bands: During 3:30 p.m. to 3:45 p.m., stock futures price bands will align with the price bands applicable during CAS. The existing dynamic price-band flexing will not apply during that period. Trading and risk systems should therefore recognise that the treatment of price bands can depend on the stage of the trading day.
Order-Level Margin Requirements: CAS orders are subject to applicable order-level margin requirements, with specified treatment for orders carried forward from CTS. If carried-forward orders are modified during CAS, applicable order-level margin requirements apply to them. Participants should not assess modification solely as a price or quantity decision. Its implications for priority and margin treatment also need attention.
Special Trading Sessions: For special trading sessions, CAS retains the prescribed duration. The also provides a sequence for the close of derivatives trading and the subsequent post-close session. Participants should follow the exchange schedule announced for the particular special session rather than assume ordinary clock timings apply.

Implementation Dates

Changes Effective from 7 December 2026: Most modifications, including the revised timings and derivatives settlement methodology, take effect from 7 December 2026. Businesses should use the preparation period to review systems, procedures, staff instructions and client communications. The announcement date should not be confused with the implementation date.
Changes Effective from 8 February 2027: The revised provisions concerning unexecuted limit and iceberg order transitions take effect from 8 February 2027. Maintaining separate implementation records for the two dates can help prevent a partial update from being treated as full compliance with the revised.

Practical Implications for Traders and Investors

Review Execution Assumptions: Traders should review strategies that depend on trading until a particular time, using a particular closing-price proxy or carrying orders into the auction. A useful exercise is to trace one planned transaction through order placement, session transition, execution and settlement. This can reveal assumptions that need to be corrected.
Check Broker Communications: Investors should read their broker’s implementation notices and platform instructions. These may explain how the revised affects available order choices, internal processing and displayed information. Understanding these details before placing an order can reduce avoidable disputes over rejected instructions or unexpected order treatment.
Maintain Appropriate Risk Controls: The changes do not guarantee profits or eliminate market risk. Derivatives remain capable of producing substantial losses, and execution may differ from expectations. Participants should reassess their assumptions while maintaining controls appropriate to their positions, liquidity requirements and capacity to bear losses.

Preparation for Brokers and Compliance Teams

System Testing: Brokers can test session transitions, instrument-specific cut-offs, order carry-forward settings and reporting. Testing should include rejected instructions and interruptions as well as successful transactions. Client-facing messages should clearly explain what happened when an instruction cannot proceed.
Staff Training and Documentation: Dealers, operations teams and support staff should understand the distinction between reference prices, closing prices and settlement prices. Internal procedures should identify responsibilities and implementation dates. Scenario-based training can help staff explain the in practical language.
Reconciliation and Reporting: Businesses should check consistency between trading screens, back-office records and client reports. Where different prices legitimately appear, their descriptions should make the reason understandable. A sample transaction review can help confirm that records remain consistent from order entry through settlement reporting.

Conclusion

SEBI’s revised CAS changes the organisation of closing-session trading, pending-order treatment and derivatives expiry settlement. Its practical significance lies in understanding the correct session, instrument, price and implementation date for each activity.

Investors and traders should review execution assumptions and broker instructions. Intermediaries should coordinate technology, operations, risk and client support before the changes take effect. Careful preparation can help reduce operational errors and improve understanding of the revised market.

Need Help with SEBI Registration or Securities Market Compliance?

Planning to establish an investment advisory or research analyst business in India? Compliance Calendar LLP can help you understand the requirements for SEBI Investment Adviser Registration, Research Analyst Registration and applicable securities market compliances. Our team can guide you through the registration process, assist with documentation and help you understand regulatory updates relevant to your business.

Get in touch with Compliance Calendar LLP today!

Call/WhatsApp: +91 9988424211
Email: info@ccoffice.in

Frequently Asked Questions (FAQ’s)

Q1. What does CAS mean?

Ans. CAS stands for Closing Auction Session. It is an auction process used to determine the closing prices of applicable securities.

Q2. When will the revised structure take effect?

Ans. Most changes take effect on 7 December 2026. The revised unexecuted-order carry-forward provisions take effect on 8 February 2027.

Q3. What are the revised CAS timings?

Ans. CAS runs from 3:30 p.m. to 3:40 p.m., with separate transition and order-entry stages. Order entry closes randomly between 3:38 p.m. and 3:40 p.m.

Q4. Do all derivatives contracts stop trading at 3:30 p.m. on expiry days?

Ans. No. The 3:30 p.m. cut-off applies to expiring index derivatives. Stock derivatives continue until 3:45 p.m., including on expiry days.

Q5. Is the CAS reference price the same as the expiry settlement price?

Ans. No. The CAS reference generally uses the final 15-minute CTS VWAP, while the revised expiry settlement methodology uses relevant final 30-minute CTS VWAP inputs.

Q6. Will the changes remove trading risk?

Ans. No. Revised trading and settlement procedures do not guarantee returns or protect participants from market losses.

Q7. Can market orders be modified or cancelled during the final CAS stage?

Ans. No. From 3:36 p.m. until random closure, market orders cannot be modified or cancelled. Only new limit orders may be entered during this stage.

Q8. Will unexecuted iceberg orders move into CAS?

Ans. Eligible iceberg orders will transition as fully disclosed limit orders unless the participant opts out when placing the original order. This provision takes effect on 8 February 2027.

Q9. How is the CAS reference price determined when no trades occur?

Ans. If no trades occur during the final 15 minutes of continuous trading, the day’s last traded price is used. If there are no trades throughout the day, the previous closing price applies, with adjustments where relevant for corporate actions.

Q10. What are the revised cash-market post-close session timings?

Ans. The post-close session will run from 3:50 p.m. to 4:00 p.m., with trades executed at the securities’ closing prices, effective 7 December 2026.

Article last updated on : 19 Oct 2026.