Relli said SEBI will extend the call auction mechanism to the opening session from September 7, mirroring the closing session process already in place. Brokers will also start accepting after-market orders between 3:15 pm and 3:20 pm, a window he said currently sits unused. He expects this change to bring in more participation from retail investors, high net worth individuals, and institutions such as mutual funds and arbitrage funds.
Relli also flagged that SEBI’s Secondary Market Advisory Committee, of which he is a member, has discussed enabling short selling and expanding the securities lending and borrowing mechanism (SLBM). He said this could drive more volume into the cash segment once implemented.
SEBI’s action on August 13 came after the regulator’s surveillance systems detected unusual order activity during the cash session. The regulator’s chairman also cautioned market participants against similar activity going forward.
Relli credited SEBI and the exchanges for identifying the pattern and acting within days. “Within a few days, they were able to figure out the manipulations and unusual volumes in the markets during the cash session,” he said. He added that surveillance tools track both buy-side and sell-side orders for unusual activity, and that brokers run their own risk checks to flag abnormal volumes.
Relli explained how the call auction session for F&O stocks currently works. Continuous trading runs from 9:15 am to 3:15 pm for the 209 stocks under the mechanism. Between 3:00 pm and 3:15 pm, a reference price is calculated using the weighted average volume method, which then feeds into the call auction session between 3:20 pm and 3:30 pm. Traders can place and modify both limit and market orders between 3:20 pm and 3:25 pm; after 3:25 pm, only limit orders are allowed. The market closes at a random point after 3:28 pm, and that price becomes the official closing price.
From September, a similar auction structure will apply to market open, running between 9:00 am and 9:10 am. Relli said several brokers have already begun accepting after-market orders ahead of the September deadline. “Most of us will not even wait for September and start doing it as fast as our systems permit,” he said.
Relli said the changes require system-level adjustments but do not add meaningfully to broker expenses. He said SEBI consulted the industry properly and gave brokers adequate time to prepare. Confusion among market participants over the new timings, rather than any system readiness issue, is what he said is currently limiting participation in the call auction session.
He also noted that derivative markets for F&O stocks remain open until 3:40 pm, ten minutes longer than before, since the underlying cash asset is not tradable during that window.
For the full interview, watch the accompanying video
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