Two commissions, one tax, every trade
A day trade is a round trip — buy and sell the same stock on the same day — and Taiwan charges for both legs of it. The broker takes a commission on the buy and another on the sell. The government takes a securities transaction tax once, on whichever leg is the actual sale. None of this is optional or negotiable away entirely: the commission rate can be discounted, but the tax cannot.
0.1425%
Standard commission rate, per leg
0.15%
Day-trade transaction tax (sell leg)
0.3%
Standard transaction tax (non-day-trade sale)
NT$20
Typical minimum commission per leg
Working example
Buy 1,000 shares at NT$100, sell at NT$102 the same day, with a 60% broker discount (6折) and a NT$20 minimum per leg:
1,000 shares, NT$100 → NT$102, 60% discount, same-day
- Buy commission: 100 × 1,000 × 0.1425% × 0.6
- NT$86
- Sell commission: 102 × 1,000 × 0.1425% × 0.6
- NT$87
- Day-trade tax: 102 × 1,000 × 0.15%
- NT$153
- Total cost
- NT$326
- Gross profit: (102 − 100) × 1,000
- NT$2,000
Net profit after costs: NT$1,674 — costs consumed about 16% of the gross move.
The same trade without the day-trade tax cut — held overnight instead — would pay NT$306 in tax instead of NT$153, since the standard 0.3% rate applies. The commission is unchanged either way; only the tax leg moves.
The breakeven price is not zero
Because both legs carry a commission and the sale carries a tax, a day trade needs the price to move in your favor by more than nothing just to come out even. That breakeven move is what the calculator reports separately from your entered exit price — it is a property of the trade size and cost structure, not of how the trade actually went.
On a small trade, the minimum fee per leg can matter more than the percentage rate. Two NT$20 minimums plus tax on a 100-share trade at NT$50 is a much larger fraction of the position than the same math on a 1,000-share trade at NT$100 — the percentage rate never even engages, because the calculated commission falls below the floor.
Comparing gross P&L instead of net
A trade that "made money" on the raw price difference can still be a net loss once both commissions and the tax are subtracted — especially on a tight stop where the price barely covered the breakeven move.
Forgetting the tax is charged on the sale, not the buy
For a short (sell-first) trade, the tax applies to the entry price, not the exit. Using the wrong leg understates or overstates the tax depending on which way the price moved between entry and exit.
Assuming the day-trade tax rate never changes
The 0.15% rate is a policy incentive, not a permanent feature of the tax code. Confirm the current rate before trading — this calculator uses the rate current at the time it was written and does not fetch it live.
Minimum tick sizes
TWSE prices move in fixed increments that widen as the price rises, which is why exchange quotes never show fractions smaller than the applicable tick — worth knowing when setting an entry or stop price.
TWSE minimum price movement (tick size) by price band
| Price (NT$) | Tick size |
|---|---|
| Under 10 | 0.01 |
| 10 – 50 | 0.05 |
| 50 – 100 | 0.1 |
| 100 – 500 | 0.5 |
| 500 – 1,000 | 1 |
| 1,000 and above | 5 |