BSE shares slide 15% since CAS implementation; Jefferies flags options hit

BSE share price:BSE shares have been under pressure since the implementation of Sebi's new Closing Auction Session (CAS) for stocks in the F&O segment.

 

On Wednesday, the stock extended its losing streak to the third straight session, slipping 3 per cent to hit an intraday low of ₹3,131.50.

 

According to ACE Equity data, BSE shares have declined over 7 per cent in the past three sessions and have tumbled 15 per cent since the CAS came into effect on August 3.

 

The 15 per cent decline has eroded BSE’s market capitalisation by ₹20,231.05 crore, data showed.

 

At the current market price (CMP), BSE shares are down 30 per cent from their 52-week high of ₹4,446.80, touched on May 27, 2026. The stock’s market capitalisation has declined by ₹44,793.83 crore from its 52-week high, when it stood at ₹1.73 trillion. CAS impact 

 

 

According to Jefferies, the introduction of CAS adversely impacted equity options turnover and contracts in August, which is negative for companies like BSE and Groww.

 

The industry's August 2026 index options premium Average Daily Turnover (ADTO) of ₹539 billion was the lowest since February 2025. Options ADTO fell 20 per cent M-o-M, led by uncertainty around CAS. Other derivative products such as index futures and stock F&O also witnessed a decline in August. 

 

Industry cash ADTO was flat on a M-o-M basis. BSE's August 2026 ADTO of ₹187 billion was down 26 per cent M-o-M due to CAS and an additional expiry in the base. Its P/N ratio increased to 12.2bps in August vs 10.9bps last month.

 

The brokerage highlighted that the key challenge with CAS has been the uncertainty on expiry day, forcing option writers to stay away from the market. 

 

"Sebi has introduced the CAS from August 2026, replacing the volume weighted average price (VWAP). This has resulted in volatility at the end of the trading day, as auction pools are currently shallow (1 per cent of cash ADTO)," Jefferies said.

 

Interestingly, BSE's cash market share rose to 8.1 per cent in the month of August, marking the second consecutive monthly rise, Jefferies noted in its report.

 

BSE stock: Technical view 

 

Harish Jujarey, AVP, head - technical equity research, Prithvi Finmart, said that BSE Ltd has remained under pressure and has corrected nearly 30 per cent from its all-time high of 4,446. Last week, the stock found some support near its 200-DMA, but in today’s session, it slipped below this key support level. At current levels, BSE trades below all the key moving averages. 

 

The next important support for the stock is now seen in the ₹3,100 - ₹3,000 zone. The RSI is near oversold levels of 30 and is showing a slight positive divergence.

 

"The ₹3,100 - ₹3,000 zone will therefore be crucial to watch. If the stock manages to hold this zone, we could see a recovery towards ₹3,500 - ₹3,550 levels. However, a decisive break below ₹3,000 could lead to further weakness and a deeper correction," he added.

 

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