On October 30, 2025, SEBI announced a new rule that will affect non-benchmark indices such as Bank Nifty and Fin Nifty. The move aims to reduce the dominance of a few large stocks within these indices. Currently, the movement of just one or two major bank stocks can trigger significant swings in the entire index. This change is expected to have a wide-ranging impact on ETFs, mutual funds, and derivative traders.
The main objective of this step is to make the index more balanced, restrict the heavy weightage of select stocks, and provide smaller banks with a fair opportunity. Let us understand what this change means for investors.
What’s Happening?
SEBI has issued new guidelines to make index compositions more balanced. From now on, any non-benchmark index or any index on which derivative contracts can be launched must include at least 14 stocks instead of the current 12. Additionally, the maximum weight of a single stock cannot exceed 20%, and the combined weight of the top three stocks cannot go beyond 45%.
This rule will directly impact the Nifty Bank index, which will now include at least two more banking stocks. Moreover, by September 2025, the weight of major stocks like HDFC Bank will have to be reduced from the current 28.49% to 20%. At present, ICICI Bank holds 24.38%, SBI has 9.17%, Kotak Mahindra Bank has 8.97%, and Axis Bank has 8.78%.
Weight Reduction Methodology
SEBI has laid out different timelines to implement these rules. For BSE’s Bankex and NSE’s Financial Nifty Index, the change will be implemented in a single phase. They must comply with the new rules by December 31, 2025.
However, for Bank Nifty, the change will be implemented gradually due to its high trading volume. SEBI does not want a sudden sell-off to cause a sharp fall in the index. Therefore, the rebalancing of Bank Nifty will take place in four phases, with the final deadline set for March 31, 2026.
For instance, if the weight of a top stock is 28% and needs to be reduced to 20%, resulting in an 8% cut, it will be done in four phases with a 2% reduction in each phase. The weight reduced from large stocks will be redistributed among smaller stocks.
Impact on ETFs and Derivatives Trading
Bank Nifty futures and options (F&O) are among the most actively traded contracts in the Indian market. SEBI’s new rules on weightage will directly influence them.
Since the rebalancing will be executed in four stages, Bank Nifty ETFs will also need to adjust their portfolios step by step. This means their exposure to HDFC Bank and ICICI Bank will decline, while allocations to PSU and mid-sized private banks will rise.
This adjustment will also affect ETFs and index-tracking mutual funds, as fund managers will need to rebalance portfolios in line with the revised index composition. In the short term, this may increase tracking error and costs.
What Does This Mean for Investors?
The proposed change by SEBI will influence investors in two key ways:
First, if you trade in derivatives, you are likely to experience lower volatility in Bank Nifty. Sudden or sharp movements in stocks like HDFC Bank or ICICI Bank will no longer cause such dramatic index swings.
Secondly, if you invest through ETFs or index funds, your fund manager will gradually shift allocations from large banks such as HDFC Bank to smaller ones like PNB or Bank of Baroda. Since SEBI has mandated a phased transition, your investments are unlikely to be impacted abruptly. Over time, index funds will become safer as their risk will not depend solely on one or two heavyweights.
What’s Next?
SEBI’s move aims to ensure a more stable and secure market environment. Stock exchanges have been instructed to fully implement these changes in Bank Nifty by March 31, 2026. While certain stocks may witness increased buying or selling in the near term, SEBI’s phased approach will ensure a smooth transition. In the future, this will result in a more balanced index for the banking sector.
Over the long term, this move will benefit not only investors but also the broader market structure by reducing concentration risk and promoting more inclusive market growth.
*The companies mentioned in the article are for information purposes only. This is not investment advice.
*Disclaimer: Teji Mandi Disclaimer
