The Securities and Exchange Board of India said on 3 September 2026 that it may propose changes to the way settlement prices for derivative contracts are determined on expiry, following the first month of operation of the Closing Auction Session in the equity cash segment. Press Release No. 53/2026 records that a consultation paper on the subject "will be issued in about a week". No change has been made; the existing methodology continues until any revision is separately notified.
Background
Until 3 August 2026, the closing price of a stock in the equity cash segment was the volume weighted average price of trades executed during the last thirty minutes of the continuous trading session. SEBI replaced that mechanism for a subset of stocks by Circular No. HO/47/11/11(3)2025-MRD-POD2/I/2765/2026 dated 16 January 2026, which introduced CAS.
The circular's own reasoning, at paragraph 2, was that CAS is the prevailing method in major jurisdictions; that it aggregates market interest into a single pool of liquidity, improving execution efficiency for large orders; that the closing price is the reference for derivatives settlement, index computation and mutual fund NAV determination and so must be fair and transparent; and that an auction gives equal and transparent access to all categories of investors, while allowing passive funds to transact at the closing price and thereby reduce tracking error.
The framework was not adopted quickly. Paragraph 3 of the circular records public comments on consultation papers dated 5 December 2024 and 22 August 2025, deliberations in SEBI's Secondary Market Advisory Committee, and subsequent feedback from stock exchanges, clearing corporations, mutual funds and foreign portfolio investors.
Structurally, CAS is a separate 20-minute session from 3:15 pm to 3:35 pm on all trading days, built from four five-minute blocks: reference price calculation and transition from the continuous trading session at 3:15 pm; an order entry period for both limit and market orders at 3:20 pm; an order entry period for limit orders only, with no modification or cancellation of market orders, at 3:25 pm; and a final block from 3:30 pm with a random close in the last two minutes. Under paragraph 4.1, CAS applies in the initial phase only to stocks on which derivative contracts are available; other securities keep the 30-minute VWAP.
Critically for the present question, paragraph 4.9.1 modified paragraphs 1.1.9 and 3.1.2.7 of Chapter 5 of the SEBI Master Circular for Stock Exchanges and Clearing Corporations dated 30 December 2024, so that the settlement price for index derivatives is the closing price of the underlying index on the day of expiry, itself based on the closing prices of the index constituents; and so that stock derivative contracts settle at a price calculated by the clearing corporations on the volume-weighted average of closing prices of the stock in the cash segment across all exchanges. Paragraph 4.9.2 required exchanges and clearing corporations to formulate a joint standard operating procedure with SEBI within 30 days of the circular.
What SEBI said
The release is short and its structure matters.
What was stipulated. SEBI records that under the January circular the closing price determined through CAS "also serves as a basis for determination of settlement prices for derivative contracts on expiry". That is the link now under examination.
What SEBI has been doing since. The release describes close engagement with stock exchanges, brokers, proprietary traders, software vendors, mutual funds, industry associations and foreign portfolio investors, to facilitate smooth implementation and address operational and other issues in the initial adoption period.
Where the feedback came from. SEBI states that during the first month of operation it received feedback and suggestions from market participants "through multiple channels, including social media and other media platforms" — an unusually candid acknowledgement of the channel in a formal release.
The identified issue. Among the issues raised, "a significant area of feedback relates to the determination of settlement prices of derivative contracts on expiry based on the closing price determined through CAS".
What happens next. Having considered the experience of the initial period and the feedback, SEBI "may be proposing certain changes in the methodology for determination of settlement prices of derivative contracts", with a consultation paper in about a week.
SEBI does not describe the change contemplated, does not identify who raised the issue, and does not commit to a specific date.
Implications for practitioners
The distinction that should govern advice this week is between a decision and a signal. SEBI has not amended the January circular, has not suspended paragraph 4.9.1, and has expressed itself in the conditional — "may be proposing". Any client note that reads the release as a change to settlement mechanics would be wrong. Expiries between now and any amendment settle on the existing basis.
That said, the release is a genuine indicator for three groups.
For clearing corporations and exchanges, the standard operating procedure contemplated by paragraph 4.9.2 is the artefact most likely to be affected, and it is a joint document formulated in consultation with SEBI. Institutions should expect the consultation paper to engage with it rather than only with the circular's headline text, and should ensure the SOP's internal change-control can absorb a revision without a long systems cycle.
For derivative market participants, the exposure is in documentation and models rather than in trading. Term sheets, risk models, margin calculators and internal valuation policies that hard-code "closing price determined through CAS" as the expiry settlement reference will need review if the methodology moves. Firms should identify now where that reference is embedded, because the identification exercise is slower than the amendment.
For fund houses and passive managers, the interaction with NAV determination deserves specific attention. The January circular's own rationale at paragraph 2.2 links the closing price to index computation and NAV; a change confined in terms to derivative settlement prices could still have consequences for tracking where index and derivative references diverge. That is precisely the kind of second-order effect a consultation response is for.
Finally, the timeline is the actionable fact. A consultation paper expected within roughly a week of 3 September 2026 implies a comment window opening shortly thereafter. Firms with a view on expiry-day price formation should be preparing the response now rather than waiting for the paper, because the substantive work — reconstructing what CAS did to expiry-day prices in August 2026 — is empirical and takes time.
Frequently Asked Questions
Does this announcement change anything for the next expiry?
No. SEBI Press Release No. 53/2026 dated 3 September 2026 announces only that a consultation paper will be issued in about a week and that SEBI may propose changes. The settlement price methodology established by paragraph 4.9.1 of the circular of 16 January 2026 continues to apply unless and until SEBI notifies an amendment.
Which stocks are currently in CAS?
Under paragraph 4.1.1 of the 16 January 2026 circular, CAS applies in the initial phase to stocks in the cash segment on which derivative contracts are available. Paragraph 4.1.2 provides that the closing price for the remaining securities continues to be determined on the volume weighted average price of trades executed in the last 30 minutes of the continuous trading session.
What are the CAS timings?
Paragraph 4.2.1 of the circular provides for a separate session of 20 minutes from 3:15 pm to 3:35 pm on all trading days, comprising a reference price calculation and transition block at 3:15 pm, an order entry period for limit and market orders at 3:20 pm, an order entry period for limit orders only at 3:25 pm, and a block from 3:30 pm with a random close in the last two minutes.