The Nifty 50 and BSE Sensex showed a rare divergence on close of trade on Monday as exchanges adopted a new auction mechanism for stocks with traded futures and option contracts.
The Nifty was up 1.6% at 24,774.30 as of 3:30 p.m. IST on Monday. The BSE Sensex closed 0.7% higher at 78,639.03.
The displayed Nifty level was the official closing level, a source familiar with the matter said, adding there was no trading glitch.
Some divergence was expected as India transitioned to the new system, the source said, speaking on condition of anonymity because they were not authorised to speak to the media.
The NSE did not immediately respond to an emailed request for comment on the discrepancy.
SEBI's new Closing Auction Session (CAS), effective Monday, replaces the earlier method of calculating closing prices for stocks in the futures and options segment.
Previously, closing prices were based on the volume-weighted average price of trades during the final 30 minutes of continuous trading. Under CAS, buy and sell orders placed near the close are matched in a single-price auction, with the resulting price becoming the official close.
The change is intended to produce a fairer and more transparent closing price by concentrating end-of-day liquidity in one auction, rather than relying on trading across the final half-hour.
"It appears to be a single, end-of-session price movement that has caused the divergence between the benchmarks," said Siddhartha Khemka, head of research for wealth management at Motilal Oswal Financial Services.
"We are waiting for a response from the NSE and other market participants are also trying to understand the anomaly and are awaiting clarification from the NSE on whether it is related to the Closed Auction Session."
