Archive · 4 Sep 2026
India's Derivatives-Cash Mismatch Drives Extreme Expiry-Day Market Volatility
India has a very large market for betting on stock prices, called derivatives, but its regular stock market is much smaller.
This difference means many trades depend on a market that may not have enough buyers and sellers.
A new Closing Auction Session was designed to make the final trading price fairer and calmer.
During its first monthly expiry, prices moved sharply and then recovered quickly.
Some people may blame the new auction system for making the swings worse.
The authors say the deeper problem is the shortage of trading in the regular stock market.
Traders who use options may need to repeatedly buy or sell shares to protect themselves, which can move prices even more.
They recommend improving cash-market liquidity and making options speculation more expensive.
The Securities and Exchange Board of India introduced the Closing Auction Session on August 3, replacing final-30-minute VWAP settlement for derivatives.
During the first monthly expiry under CAS, the Sensex's indicative price fell about 2,200 points before recovering most of the decline.
One BSE options contract reportedly surged 4,000% before falling close to zero.
India's index-derivatives notional turnover can reach 300 to 400 times cash-market turnover on normal days and 3,000 times on expiry days.
The authors argue that deeper cash-market liquidity and costlier options speculation are needed to reduce expiry-day instability.
- Who
- The Securities and Exchange Board of India, derivatives traders, and the authors Raja Reddy Bujunoori, Sumit Saurav, and Venkatesh Panchapagesan.
- What
- India's new Closing Auction Session experienced sharp expiry-day price swings, highlighting a mismatch between derivatives and cash-market liquidity.
- When
- CAS began on August 3; the first monthly expiry under the system occurred on the last Thursday of August.
- Where
- In India's equity markets, including the Sensex and BSE options markets.
- Why
- The authors attribute the instability mainly to the much larger scale of derivatives trading relative to the thinner cash market.
Auction-System Concern
Structural-Mismatch Explanation
Cause of the price swings
Auction-System Concern
The sharp movements during the first CAS expiry suggest that the new auction system may have amplified market volatility.
Structural-Mismatch Explanation
The authors argue that the main cause is the much larger scale of derivatives trading compared with the relatively thin cash market.
What should be changed
Auction-System Concern
The closing-auction mechanism may need to be reset or redesigned to improve participation and reduce price impact.
Structural-Mismatch Explanation
Changing the final trading window alone will not solve the problem; cash-market liquidity must increase and options speculation must become more expensive.
Market manipulation risk
Auction-System Concern
A poorly attended auction may leave the closing price vulnerable to trades that influence index-settlement levels.
Structural-Mismatch Explanation
The authors say the broader mismatch makes manipulation possible because relatively small cash-market trades can affect contracts worth much more.
- New mechanism
- The Closing Auction Session began on August 3, with closing orders matched in one window at a single price.
- Indicative-price movement
- The Sensex's indicative price fell about 2,200 points during the first monthly-expiry auction before recovering most of the loss.
- Options volatility
- One BSE options contract rose by 4,000% before crashing toward zero.
- Normal-day mismatch
- Index-derivatives notional trading is typically 300 to 400 times the turnover in underlying shares.
- Expiry-day mismatch
- The ratio can reach as much as 3,000 on expiry days.
- CAS participation
- Less than 5% of daily trading activity now flows through CAS, compared with about 10% before the transition.
- Proposed responses
- The authors recommend easier short selling in the cash market and measures that make options speculation more expensive.