MUMBAI — The National Stock Exchange on February 18 issued a circular revising margins for select futures and options contracts. Stocks where the top 10 clients control over 20% of the market-wide position limit will face an additional 15% exposure margin in the equity derivatives segment from the March series.

“Additional exposure margin @15% in equity derivatives segment shall be levied on securities in which top 10 clients account for more than 20% of MWPL,” the NSE circular states. If additional surveillance margins already apply to a stock, the exchange will charge whichever rate is higher.

The NSE will use three months of rolling data to identify affected stocks. It plans monthly reviews to update the list. Vodafone Idea, DLF, RBL Bank, Bandhan Bank, Aurobindo Pharma, Glenmark Pharmaceuticals, NMDC, Steel Authority of India and Manappuram Finance top the initial roster of 18 stocks facing the hike.

The full list also covers Aditya Birla Capital, Container Corporation of India, Crompton Greaves Consumer Electricals, JSW Energy, LIC Housing Finance, NBCC (India), Patanjali Foods, Sammaan Capital and Indus Towers, according to the exchange.

This measure aims to curb concentration risk in F&O trading. High client dominance in positions has prompted regulators to tighten rules. Traders will need more capital for these contracts, potentially cooling speculative activity.

In a related development, the NSE announced the removal of extra margins on commodity futures. A 3% additional levy on gold contracts ends February 19. Silver futures shed their 7% extra margin on the same date. The change, detailed in a separate release, eases pressure on metal traders ahead of the expiry cycle.

Market participants welcomed the commodity relief. Gold and silver futures had borne the surcharges amid volatility in global prices. The equity F&O changes, however, signal stricter oversight on popular stocks.

Vodafone Idea shares, already volatile, drew attention after recent gains. DLF and RBL Bank, key realty and banking names, now face higher costs for derivatives positions. Bandhan Bank and others in the list have seen elevated trading volumes.

The NSE’s move aligns with efforts by India’s securities regulator to enhance market stability. Position limits prevent excessive use. Top client thresholds help spot potential manipulation risks early.

Traders must adjust strategies before March. The exchange will notify any monthly changes via circulars. For now, the 18 stocks bear the brunt of the 15% hike.

Broader markets showed caution Friday. The Sensex shed 140 points, closing below recent highs. Nifty slipped under 25,800 as financials and FMCG stocks weighed on indices.