What is an index fund, and why do so many people recommend them?
An index fund gives up on beating the market and simply owns it. That sounds like surrender. Over long periods it has been one of the more reliable decisions available to an ordinary investor.
Last checked August 2026. Sources listed at the end.
The short version
- An index fund copies a published list of companies, such as the Nifty 50, in the same proportions.
- Nobody is choosing stocks, so the fee is very low. SEBI capped index funds and ETFs at 0.90% from April 2026, and good ones charge far less.
- You accept the market return instead of trying to beat it.
- The number to compare is , not last year return.
- It removes the risk that your fund manager is wrong, which is a real and common risk.
What an index is
An index is a published list of companies, weighted by size, used to represent a market. The Nifty 50 is fifty large companies on the NSE. The Sensex is thirty on the BSE. The Nifty 500 is a much wider slice of the Indian market.
The list is not permanent. Companies that shrink or fail drop out, and growing companies come in, according to published rules. That matters more than it sounds: an index quietly removes its losers and adds its winners without anyone having to make a judgement call.
An index fund simply buys every company in the list, in the same proportion. If a company is 8% of the index, it is roughly 8% of the fund. When the index changes, the fund changes to match.
Why doing nothing clever tends to win
The argument is arithmetic before it is anything else. All the investors in a market collectively own the market, so collectively they earn the market return, before costs. After costs, the average actively managed rupee must therefore earn less than the market. Not because managers are unintelligent, but because they are most of the market and they charge fees.
That does not mean no manager beats the index. Some do. The difficulty is identifying which ones in advance, and the honest answer is that past performance is a weak guide. Funds at the top of the table often drift toward the middle within a few years, because the conditions that suited their style change.
An index fund sidesteps the question entirely. There is no manager to be right or wrong, no style to fall out of favour, and no chance that the person whose record you bought leaves the firm.
Cost, and what SEBI changed in 2026
Because nobody is researching companies, an index fund is cheap to run. Under the SEBI (Mutual Funds) Regulations, 2026, effective 1 April 2026, the cap for index funds and ETFs was reduced from 1.00% to 0.90%, and that figure now excludes statutory levies, which are charged separately.
The cap is a ceiling, not a price. Competitive Nifty 50 index funds in charge a small fraction of it. The gap between a 0.2% index fund and a 1.7% active fund is 1.5 percentage points a year, every year, compounding against you in the active fund.
The number actually worth comparing
Two index funds tracking the same index should deliver almost the same thing, so last year returns tell you very little. What tells you something is : how closely the fund keeps up with the index it copies.
A gap opens because of fees, cash held to meet withdrawals, and the cost of trading when the index changes. Lower tracking error means the fund is doing its one job well. Together with the , it is close to the entire analysis.
What an index fund does not do
It is worth being clear about the limits, because index funds are sometimes recommended with more enthusiasm than accuracy.
- It does not protect you in a crash. If the Nifty falls 35%, your Nifty index fund falls about 35%. There is no manager stepping aside. Diversification across fifty companies does not help when everything falls together.
- It cannot beat the market. By design. If that bothers you, an index fund is not what you want.
- It is concentrated in large companies. The Nifty 50 leans heavily toward a few large sectors, particularly financials. That is a real exposure, not a neutral one.
- Index does not mean safe. A small cap index fund is an index fund and is also volatile enough to fall by half.
For a beginner, a broad large cap index such as the Nifty 50 or a wider Nifty 500 fund is the usual starting point. Sector and thematic index funds exist and are a different, narrower bet.
Index fund or ETF?
Both track an index. The difference is how you buy them.
| Index fund | ||
|---|---|---|
| How you buy | Directly from the fund house | On the exchange, like a share |
| Needs a | No | Yes |
| Price you pay | End of day | Live market price, which can differ slightly from NAV |
| Monthly | Simple and automatic | Possible but clumsier |
| Typical cost | Very low | Often slightly lower still |
For someone investing a fixed amount monthly and not wanting to think about it, the index fund is usually the better fit. ETFs are covered separately.
What to remember
- An index fund copies a published list of companies rather than trying to choose winners.
- After costs, the average actively managed rupee must earn less than the market. That is arithmetic, not opinion.
- SEBI cut the index fund and ETF fee cap to 0.90% from April 2026, and competitive funds charge far less.
- Compare expense ratio and tracking error. Ignore last year return between funds tracking the same index.
- An index fund falls exactly as far as its index in a crash. It is low cost, not low risk.