# Sebi’s new closing auction rattles F&O traders, volumes plunge 2026-08-10T01:54:46+00:00 | Business & Economy | Indian Opinion Desk Corroboration: 1 independent outlet The Securities and Exchange Board of India's (Sebi) new closing auction session (CAS) for 208 derivatives stocks has caused a sharp drop in futures and options (F&O) volumes in its first week. Average traded volumes of Nifty and Bank Nifty index futures fell 40% to 69,982 contracts in the week ended 7 August from 134,754 contracts the previous week, according to NSE data. Weekly index options volumes also declined. The auction, which replaced the half-hour volume-weighted average price, determines a single closing price based on orders placed between 3.20 pm and 3.30 pm. Limited participation from arbitrageurs and retail investors has led to thin liquidity and volatile spreads. Sebi told brokerages the system will not be rolled back, calling the issues teething problems. Goldman Sachs noted weaker-than-expected participation left liquidity thinner than anticipated. Zerodha estimates the system could reduce industry earnings by 1% to 5%. ## Coverage - livemint.com - timesofindia.indiatimes.com Tags: arbitrage funds, closing auction, F&O, market reform, Nifty, SEBI Canonical: https://indianopinion.org/sebis-new-closing-auction-hits-fo-volumes-arbitrage-funds/ License: Summary and commentary (c) Indian Opinion, reusable with attribution. Facts belong to the linked sources. Cite: https://indianopinion.org/sebis-new-closing-auction-hits-fo-volumes-arbitrage-funds/#story-in-brief Review state: restored archive article, accurate at time of publication, not offered to search indexes.