Lesson 7 of 11 · Fund Mechanics · 1 min read
Tracking Difference
intermediate
The real, measured gap between what the fund actually returned and what its benchmark returned.
TER tells you the *stated* annual cost. Tracking difference tells you what actually happened: the fund's realized return minus the benchmark's realized return, over the same period. In an ideal world these would be identical (fund return = benchmark return - TER), but real funds also earn securities-lending income, incur trading/rebalancing costs, and face sampling effects — any of which can make the real gap larger or, sometimes, smaller than TER alone would suggest.
The benchmark's return is the theory. Tracking difference is what you actually got paid.
Tracking Difference
Fund's Actual Return - Benchmark's Return
A fund with a 0.10% TER but -0.25% tracking difference is costing you more, in practice, than the sticker TER implies.
What eats into the gap between benchmark and fund
1
Benchmark Return
The index itself, on paper
2
- TER, trading costs
+ securities-lending income
3
Fund's Actual Return
What you really got
Key takeaways
- This is the more honest, complete measure of a fund's real cost — TER is a useful shortcut, but tracking difference is what actually happened to your money.
- A consistently *positive* tracking difference (fund beating its benchmark) does happen — usually from securities-lending revenue the fund passes back — and isn't a red flag, just worth understanding why.