The second day of the new Closing Auction System (CAS) left investors disappointed as the Nifty 50 opened lower, wiping out yesterday’s gains and ending 159 points down. The index finished at 24,615 after a 151‑point jump in the final minutes of trading.
The Sensex behaved more calmly, opening with slight gains and closing 0.3 % lower at 78,429. Market experts said that differences between exchanges are expected to moderate as participation and liquidity grow, although occasional divergences may continue.
Turnover figures showed the NSE’s CAS handled Rs 1,542 crore, capturing 99.4 % of the market share, while the BSE’s CAS traded only Rs 9.4 crore, a 0.6 % share.
The CAS impact was especially visible in option contracts, as the day was the weekly expiry for the Nifty 50. The 24,600‑point put, trading above Rs 100 at 3:24 pm, became worthless by close, while the 24,500‑point call, priced at about Rs 30 at 3:15 pm, surged almost five‑fold.
Traders who had expected premiums to decay were caught off guard by the 150‑point rise in the cash close, which turned call writers’ and put writers’ positions into real losses.
Rajesh Palviya, Head of Research at Axis Securities, warned that with open interest around 33 lakh shares for at‑the‑money calls, the auction move translates into tangible P&L damage. He advised traders to close positions earlier on expiry‑sensitive names.
The episode underscores the need for market participants to understand that the official settlement is determined by the auction, not the 3:15 pm price, especially on expiry days.