For much of the first week of trading under India’s new auction system to set closing stock prices, traders were convinced that one of the most consequential market structure reforms in years was faltering.

As calls grew louder for the mechanism to be rolled back, the regulator met with some of the nation’s top stock brokerages and delivered a clear message: the closing auction is here to stay.Senior officials at the Securities and Exchange Board of India, including board member K.V.R Murty, told market players the new system is just facing teething issues in its early days and that the regulator remains confident that it will improve as participation rises, according to people familiar with the discussions, who asked not to be identified because the talks were private.

The discussions came after the first two trading sessions — including Tuesday’s expiry on the National Stock Exchange of India Ltd. — under the new system produced unexpected swings that led to market-wide confusion. Brokerages were fielding questions from clients, while retail investors took to social media as they struggled to understand why official closing prices appeared disconnected from the day’s trading.The new price-setting method, covering more than 200 stocks with listed derivatives, was first proposed by SEBI in 2024 after major index-tracking funds sought a closing auction to reduce tracking errors. It is designed to improve price discovery and align India’s market structure with major global exchanges, according to the regulator.In meetings held on Tuesday and Wednesday, SEBI urged brokerages to speed up technology upgrades and boost order flow so the auction could operate as intended.A spokesperson for SEBI didn’t respond to an email seeking comment.Much of the volatility is probably driven by weak participation. Many proprietary trading firms and high-frequency traders, which provide liquidity on expiry days, either stayed away from the auction or reduced activity as the new system settled in.“Allowing some time for liquidity to develop before shifting to closing auction may have facilitated a smoother transition,” said Mayank Sachan, chief executive officer of Zenskar Research. The proprietary trading firm has reduced its expiry-day strategies tied to index options, he said.The lack of participation left liquidity thinner than expected, Goldman Sachs Group Inc. said in a note to clients. As a result, modest buy and sell orders were able to move the equilibrium price by much more than traders were used to seeing. The official closing price is used to settle stock and index derivatives, making those swings significant.“Every developed market has a closing auction. We just got there before the liquidity did,” said Bhautik Ambani, chief executive officer of AlphaGrep Mutual Fund, a unit of the quantitative trading firm AlphaGrep.Volume Hit