SEBI Closing Auction: Arbitrage Funds Face Return Squeeze

SEBI's Closing Auction Session Changes How Indian Markets Price the Close The Closing Auction Session (CAS) went live today across all F&O-eligible stocks on Indian exchanges. The old mechanism — a 30-minute weighted average price window that ran from 3:00 PM to 3:30 PM — is gone. In its place is a call auction: orders accumulate during a brief window, then clear at a single equilibrium price. It's a structural change that aligns India's close with how London, Hong Kong, and most developed markets have operated for years. The immediate question for investors isn't whether this is a better price-discovery mechanism in theory. It clearly is. The real question is what happens to the ₹1.5–2 lakh crore sitting in arbitrage mutual funds that built their edge, at least partly, around the old system's predictable inefficiencies. Arbitrage funds exploited the 30-minute VWAP window by positioning in cash and futures markets to capture the spread between spot and futures prices as the close approached. The new auction format compresses that window and introduces genuine price uncertainty at close. Funds that relied on this as a near-riskless return kicker will need to rework their playbooks. Impact on Arbitrage Funds and AMC Stocks The funds most exposed to this shift are large arbitrage schemes. [MOFSL](/stock/MOFSL) and [HDFCAMC](/stock/HDFCAMC) both run significant arbitrage AUM. HDFCAMC's arbitrage fund alone managed approximately ₹24,000 crore as of recent disclosures. [Nippon Life India Asset Management](/stock/NIPPONLIFE) runs one of the larger arbitrage schemes in the category. These are businesses where incremental basis points matter — arbitrage funds typically return 50–150 bps above liquid funds annually, and the margin of safety is thin. The concern isn't that arbitrage funds collapse. Arbitrage opportunities still exist in the cash-futures spread, in index rebalancing events, and in corporate actions. But the closing price mechanism contributed meaningfully...