SEBI revises Closing Auction Session timings, retains 30-min VWAP for expiry-day settlement
Synopsis
SEBI has finalised a revamped Closing Auction Session framework — new timings, structured order windows, and a phased rollout starting December 2026 — while keeping the 30-minute VWAP for expiry-day derivatives settlement intact. The simultaneous moves on depositary rules and graded broker compliance suggest a broader microstructure reset is underway.
Key Takeaways
SEBI issued the final Closing Auction Session (CAS) framework on 15 October 2026 , revising timings to 3:30 pm – 3:40 pm .
The 30-minute VWAP methodology for expiry-day settlement of index and stock derivatives has been retained.
Most provisions take effect from 7 December 2026 ; iceberg and unexecuted limit order transition rules kick in on 8 February 2027 .
Expiring index derivatives contracts will stop trading at 3:30 pm on expiry days ; stock derivatives continue until 3:45 pm .
SEBI is also reviewing depositary regulations for fraud prevention and exploring graded compliance requirements for brokers.
The Securities and Exchange Board of India (SEBI) on Thursday, 15 October 2026 issued a final framework for the Closing Auction Session (CAS) in the equity cash market, revising its timings and operational structure while retaining the existing 30-minute volume-weighted average price (VWAP) methodology for determining expiry-day settlement prices of both index and stock derivatives. The new framework is set to take effect in two phases, beginning 7 December 2026.
Revised CAS Timings and Structure
Under the revised framework, the CAS will operate from 3:30 pm to 3:40 pm on all trading days. The session opens with a one-minute reference-price calculation and transition period from 3:30 pm to 3:31 pm. Both limit and market orders will be accepted from 3:31 pm to 3:36 pm. After that window, only limit orders will be permitted, and market orders cannot be modified or cancelled. The session will then close randomly between 3:38 pm and 3:40 pm, after which order matching takes place.
Derivatives Trading and Expiry-Day Rules
Index derivatives will continue trading until 3:45 pm on normal trading days. However, expiring index derivatives contracts will stop trading at 3:30 pm on expiry days. Stock derivatives will trade until 3:45 pm, including on expiry days. The cash market's post-close session will run from 3:50 pm to 4:00 pm, with all trades executed at closing prices. The decision to retain the 30-minute VWAP methodology for expiry-day settlement followed a consultation paper process that reviewed concerns around derivatives settlement pricing.
Two-Phase Implementation
Most provisions of the new framework will come into force on 7 December 2026. An exception applies to provisions governing the transition of unexecuted limit and iceberg orders from the continuous trading session — those rules will take effect from 8 February 2027, according to the regulator's notification. The phased rollout is designed to allow exchanges and market participants adequate preparation time.
Broader Regulatory Agenda
Alongside the CAS changes, SEBI is reviewing regulations governing depositories and their participants, with an eye on simplifying existing rules and strengthening fraud prevention. For brokers, the regulator is reportedly exploring graded compliance requirements based on their scale, client exposure, and technology dependence. Separately, SEBI is addressing concerns over transactions — including tender offers, buybacks, and offers for sale — that currently fall outside the interoperability framework.
The comprehensive overhaul signals SEBI's intent to tighten market microstructure even as it works to reduce compliance friction for smaller brokers, a dual push that market participants will be watching closely as implementation deadlines approach.
Frequently Asked Questions
What is the revised Closing Auction Session timing announced by SEBI?
SEBI has revised the Closing Auction Session to operate from 3:30 pm to 3:40 pm on all equity cash market trading days. The session includes a structured sequence: a one-minute reference-price window, an order entry period, and a randomised close between 3:38 pm and 3:40 pm followed by order matching.
Why has SEBI retained the 30-minute VWAP for expiry-day settlement?
SEBI retained the 30-minute volume-weighted average price methodology after a review and consultation paper process examining concerns about derivatives settlement pricing on expiry days. The decision preserves a broader pricing window to limit last-minute price distortion in index and stock derivatives.
When will SEBI's new CAS framework take effect?
Most provisions of the new CAS framework will take effect from 7 December 2026. Provisions governing the transition of unexecuted limit and iceberg orders from the continuous trading session will come into force later, on 8 February 2027.
How will expiry-day trading in derivatives change under the new rules?
Expiring index derivatives contracts will stop trading at 3:30 pm on expiry days under the new framework. Stock derivatives, however, will continue trading until 3:45 pm even on expiry days. On normal trading days, both index and stock derivatives will trade until 3:45 pm.
What other regulatory changes is SEBI working on alongside the CAS revisions?
SEBI is reviewing regulations for depositories and their participants to simplify rules and bolster fraud prevention. It is also exploring graded compliance requirements for brokers based on scale, client exposure, and technology use, and is addressing gaps in the interoperability framework covering tender offers, buybacks, and offers for sale.
