Within a month of launching the Closing Auction Session, SEBI is preparing a consultation paper to rework how futures and options contracts are settled at expiry. The CAS, designed to stabilise closing prices, triggered unexpected volatility on expiry days, raising concerns about price manipulation and settlement integrity. SEBI now plans to examine whether F&O contracts should be settled using CAS-derived prices or an alternative mechanism, signalling that the new closing price framework may need structural refinement.

The Closing Auction Session is a price-discovery mechanism where buy and sell orders are collected during a defined window and matched at a single equilibrium price, replacing the earlier volume-weighted average price method for determining the official closing price of securities. SEBI introduced CAS to reduce end-of-day manipulation and align India with global best practices used in exchanges like NSE, BSE, LSE, and NYSE.

However, the interaction between CAS and F&O expiry settlement exposed a structural tension. On expiry days, derivatives contracts are settled against the closing price of the underlying. When CAS itself becomes volatile — because large expiry-day positions create order imbalances during the auction window — the settlement price can swing significantly, harming retail investors and undermining the very stability CAS was meant to deliver.

SEBI's proposed consultation will likely explore options such as using a separate VWAP-based settlement price distinct from the CAS price, adjusting the CAS window on expiry days, or imposing additional circuit filters. This directly tests SEBI's core mandate under SEBI Act, 1992 — market integrity and investor protection. For aspirants, this event connects the static concepts of price discovery, settlement mechanisms, and the regulatory consultation process (SEBI's standard tool before issuing binding circulars).