Trading costs, fees and tax drag
Cost drag is the single most underestimated variable in retail trading. It is small per trade, relentless in aggregate, and it is charged whether the trade wins or loses.
Where the money goes
- Spread — the gap between bid and ask, paid on entry and exit.
- Commission — a flat or per-share fee at both ends.
- Slippage — the difference between the intended and executed price, worst exactly when markets move fast.
- Financing — daily interest on leveraged or margined positions.
- Taxes — short-term rates on realised gains, with no long-term relief.
Why it compounds
A trader making ten round trips a day pays that stack twenty times daily. Even a tiny per-trade cost becomes a large annual hurdle: the required gross win rate rises with frequency, while the achievable edge does not. This is exactly why the Taiwan data shows traders who look profitable gross and still finish behind a passive index net of costs.
The comparison that matters
A diversified index fund charges a fraction of a percent per year, once. That is the benchmark every active strategy must clear before it has produced anything. See is day trading worth it? for the full comparison.
Frequently asked questions
Do zero-commission brokers remove the cost problem?
No. Zero-commission brokers still earn from the spread and, in some markets, from payment for order flow. The cost moves; it does not disappear.
How much does slippage matter?
More than most traders assume, because it is worst during fast markets — precisely when short-term strategies trade most.
Are taxes really that significant?
Yes. Short-term gains are taxed at the highest marginal rate in most jurisdictions, while long-term holders defer tax for years and often pay a lower rate.
Read the whole argument
The arithmetic of cost drag is worked through in full in Day Trading Kills.