Tracking Difference vs Tracking Error: Which One Really Decides Index Fund Returns?
Blog by Aliceblue News Desk
20 October 2026
9 minutes
Two Nifty 50 index funds can track the same index, charge similar fees and still give slightly different returns. Why? One reason is the difference between tracking difference and tracking error. The terms sound similar, but they measure different things.
Tracking difference tells you how far the fund’s return was from the benchmark. Tracking error tells you how consistently the fund stayed close to that benchmark.
If you want to understand how much of the index return actually reached your portfolio, tracking difference is the more direct measure.
Quick Answer
Tracking difference is the gap between an index fund’s return and its benchmark return. Tracking error measures how much that gap changes over time. If the Nifty 50 TRI earns 12% and your fund earns 11.6%, the tracking difference is -0.4%. A lower tracking error means the fund follows the index more consistently. For choosing an index fund, check both.
Table of Contents
- What Is Tracking Difference?
- What Is Tracking Error?
- Tracking Difference vs Tracking Error
- Which One Matters More for Index Fund Returns?
- Practical Example With ₹5 Lakh
- Why Do Tracking Gaps Happen?
- Tracking Difference vs Expense Ratio
- What Is a Good Tracking Error?
- Which Period Should You Check?
- How to Compare Two Index Funds
- Index Funds vs ETFs: One Extra Check
- Common Mistakes to Avoid
- Tips for Beginner Index Fund Investors
- Conclusion
- Frequently Asked Questions
What Is the Tracking Difference?
Tracking difference measures the difference between a passive fund’s return and the benchmark it tracks.
The basic formula is:
Tracking Difference = Fund Return − Benchmark Return
Suppose:
- Nifty 50 TRI return: 12%
- Index fund return: 11.6%
Tracking difference:
11.6% − 12% = -0.4%
The fund underperformed the benchmark by 0.4 percentage points. Value Research also defines tracking difference as the gap between the return of a passive fund and its underlying benchmark.
Can Tracking Difference Be Positive?
Yes. If the benchmark returns 10% and the fund returns 10.1%, the tracking difference is +0.1%. But index funds are designed to replicate an index rather than beat it consistently. Because the fund has expenses and may temporarily hold cash, tracking difference is often slightly negative over longer periods.
What Is Tracking Error?
Tracking error measures how consistently an index fund follows its benchmark. SEBI defines it as the annualised standard deviation of the difference between the daily returns of the fund and its underlying index. That sounds technical.
A simpler way to understand it is: Tracking error tells you how much the return gap keeps moving around.
Example:
Consider two funds.
Fund A’s gaps from the benchmark:
- -0.3%
- -0.4%
- -0.3%
- -0.4%
The gap is fairly stable.
Fund B’s gaps:
- +0.2%
- -1.0%
- +0.4%
- -0.8%
Fund B’s gap moves around much more.
So Fund B would generally have a higher tracking error.
Tracking Difference vs Tracking Error
Factor | Tracking Difference | Tracking Error |
What it measures | Return gap | Variation in the return gap |
Main question | How much did the fund lag or beat the index? | How consistently did it track the index? |
Directly linked to delivered return? | Yes | Indirectly |
Can be positive or negative? | Yes | No |
Lower is better? | A smaller negative gap is generally better | Lower is generally better |
Best use | Comparing actual return delivery | Comparing tracking consistency |
The easiest way to remember it is:
- Tracking difference = size of the gap
- Tracking error = stability of the gap
Which One Matters More for Index Fund Returns?
Suppose two funds track the same index.
Fund A | Fund B | |
Benchmark CAGR | 13.0% | 13.0% |
Fund CAGR | 12.7% | 12.3% |
Tracking difference | -0.3% | -0.7% |
Tracking error | 0.18% | 0.12% |
Fund B has lower tracking error.
Its tracking may have been more consistent. But Fund A delivered a return much closer to the index.
So if your question is: “How much benchmark return actually reached me?”
Fund A did better in this example.
This shows why you should not choose an index fund using tracking error alone. A fund can consistently lag its benchmark and still have low tracking error.
Practical Example With ₹5 Lakh
Suppose two index funds track the same benchmark.
You invest ₹5 lakh for 10 years.
Assume:
- Fund A return after tracking gap: 11.7% a year
- Fund B return after tracking gap: 11.4% a year
After 10 years:
Fund A: about ₹15.12 lakh
Fund B: about ₹14.72 lakh
Difference:
about ₹40,000
A gap of only 0.3 percentage points a year can therefore add up over long periods.
That is why tracking difference matters to long-term investors.
Why Do Tracking Gaps Happen?
An index fund cannot always copy its benchmark perfectly.
SEBI scheme disclosures list several reasons for tracking error and tracking difference.
1. Expense Ratio:
The benchmark does not pay fund-management expenses. The fund does. That naturally creates some gap.
2. Cash Holdings:
Funds may temporarily hold cash for:
- Redemptions
- Fresh investments
- Expenses
- Corporate actions
Cash may earn a different return from the index.
3. Rebalancing:
When the index adds or removes a stock, the fund must adjust its portfolio. The fund may not be able to trade at exactly the same price used by the index.
4. Transaction Costs:
Buying and selling securities creates costs that the index itself does not bear in the same way.
5. Liquidity:
If a stock is difficult to trade, the fund may struggle to match the index weight immediately.
6. Corporate Actions:
Dividends, rights issues, mergers, and other company events can temporarily create differences.
Tracking Difference vs Expense Ratio
A common mistake is choosing the cheapest index fund automatically.
Suppose:
Fund A | Fund B | |
Expense ratio | 0.15% | 0.10% |
Tracking difference | -0.30% | -0.45% |
Fund B has the lower expense ratio.
But Fund A has historically delivered returns closer to the benchmark.
Why?
Because tracking difference reflects more than the published expense ratio.
It can also capture:
- Cash drag
- Rebalancing
- Transaction costs
- Execution quality
- Portfolio-replication differences
So expense ratio matters, but it should not be your only filter.
What Is a Good Tracking Error?
For a passive fund, lower tracking error is generally preferable.
SEBI’s current framework states that, for applicable index funds and ETFs, annualised tracking error based on past one-year rolling daily data generally should not exceed 2%, except in circumstances beyond the AMC’s control.
But 2% should not be treated as a target.
When two funds track the same index, you would generally prefer the fund with consistently lower tracking error, provided tracking difference, costs and other factors are also reasonable.
AMFI publishes scheme-wise tracking error and tracking difference data, which investors can use for comparison.
Which Period Should You Check?
Avoid making decisions based on one month.
Tracking difference is more useful when viewed across longer periods such as:
- 1 year
- 3 years
- 5 years
- Since inception
SEBI requires tracking-difference disclosures for multiple periods on AMC and AMFI websites.
A temporary rebalance or large inflow can affect a short period.
Longer periods give you a better picture of how efficiently the fund has actually tracked its benchmark.
How to Compare Two Index Funds?
When two funds track the same benchmark, use this simple checklist.
- Compare Tracking Difference: Check which fund has historically delivered returns closer to the benchmark.
- Check Tracking Error: Then see which fund has tracked the index more consistently.
- Compare Expense Ratio: Lower costs are useful when tracking quality is similar.
- Check Fund History: A newly launched fund may not have enough history to judge tracking quality properly.
- Make Sure the Benchmark Is the Same: Do not compare a Nifty 50 fund with a Nifty Next 50 fund just because both are called index funds.
For passive mutual-fund options, you can also explore Alice Blue Index Funds.
Index Funds vs ETFs: One Extra Check
Tracking difference and tracking error apply to both index funds and ETFs.
But ETFs have another issue: market price.
An ETF trades on a stock exchange, so the price you actually buy or sell at can be above or below its NAV.
Zerodha highlights that ETF investors should also watch:
- Trading liquidity
- Bid-ask spread
- Premium or discount to NAV
because a low tracking error at NAV level does not automatically guarantee a good execution price for the investor.
For a normal index mutual fund, you generally transact at NAV rather than an exchange-traded market price.
Common Mistakes to Avoid
- Treating Tracking Error and Tracking Difference as the Same Thing: They answer different questions.
- Looking Only at Tracking Error: A fund can track consistently but still lag the index by a relatively large amount.
- Choosing Only by Expense Ratio: The cheapest fund is not automatically the best tracker.
- Comparing Different Benchmarks: Only compare tracking metrics between funds following the same index.
- Using the Wrong Index Return: For equity index funds, compare against the relevant Total Return Index, or TRI, where applicable, because TRI includes dividends.
- Reacting to Short-Term Gaps: One unusual month does not prove that a fund is badly managed.
Tips for Beginner Index Fund Investors
- Choose the index first.
- Compare funds tracking that same benchmark.
- Look at long-term tracking difference.
- Check tracking error for consistency.
- Compare expense ratios after tracking quality.
- Use TRI for a fair return comparison.
- Check AMFI or AMC disclosures.
- For ETFs, also check liquidity and bid-ask spread.
- Avoid switching funds because of tiny short-term differences.
- Look for consistent tracking quality over time.
Conclusion
Tracking difference and tracking error measure two different parts of index-fund performance.
Tracking difference tells you how far the fund’s return was from the benchmark.
Tracking error tells you how consistently the fund stayed close to the benchmark.
For understanding the return that actually reached your portfolio, tracking difference is more direct. But a well-run passive fund should ideally have both a small tracking difference and low tracking error.
When comparing index funds tracking the same benchmark, look at tracking difference first, tracking error next, and then expense ratio and other practical factors.
Frequently Asked Questions
Blog by Aliceblue News Desk
