Direct answer: what to check
For an STP (straight-through processing) broker, the most useful starting point is to separate published pricing from variable execution outcomes. Published pricing usually includes what you pay per trade (for example, spreads and commissions) and any additional trade-related fees. Variable outcomes include what spread you actually receive at execution and whether you experience execution differences such as slippage.
Because STP can still route orders and fill them under different market and operational conditions, you should verify the total cost components that the broker discloses, then treat the final trading cost as partly uncertain.
Mechanism: define “fees” and “spreads”
A spread is the difference between a quoted buy (ask) and sell (bid) price shown at a point in time. When you trade, you do not directly “pay a spread” as a separate line item; instead, the spread is reflected in your entry and exit prices.
A commission is a separate charge per trade or per unit traded, often disclosed alongside the spread.
Other trade-related fees may include costs tied to specific order types, account features, or inactivity/administrative charges. Even when these are not called “execution fees,” they affect the overall economics of trading.
For STP, the core mechanical idea is that orders are transmitted for execution without manual intervention. However, that does not remove market variability: the price you receive depends on market conditions and how the order meets liquidity.
Evidence or example: estimate total cost with explicit assumptions
To compare brokers without needing real-time data, you can use a simple framework with clear assumptions:
- Assume a typical round-trip involves a buy and a sell.
- Use the broker’s published spread model (for example, whether they describe it as fixed or variable, and how they define it).
- Add any disclosed commission per trade (or commission per lot/unit).
- Include any explicit trade charges that apply per trade or per volume.
Example (illustrative, not a live quote):
- Assume you trade an amount where the commission is C per side.
- Assume the spread at execution is S per side, expressed in the same units.
- Then a rough total cost estimate is 2×S + 2×C, plus any other per-trade fees.
This estimate is only as good as the assumptions. In practice, the spread you experience at the moment of execution can differ from how it is described in marketing materials, especially during fast market moves.
Limitations and risks: where checks can still fail
A material limitation is that published pricing does not fully determine realized execution. Even with transparent spreads and commissions, execution can vary due to:
- Slippage / price movement: if the market moves between the time you submit and the time the order is filled, the effective entry/exit can differ.
- Ambiguous pricing definitions: some disclosures describe spreads using representative conditions without explaining how spreads behave during volatility.
- Unclear fee scope: administrative charges, inactivity fees, funding-related costs, or fees tied to specific account features can change the effective cost profile.
- Failure mode—missing components: comparing only spreads while ignoring commissions and other trade charges can produce an incorrect cost comparison.
Verification and next questions
To verify costs independently, focus on what the broker publishes for your exact account type and for the order/transaction types you plan to use. Then ask:
- Which costs are charged per trade (spread vs commission vs explicit fees), and how are they calculated?
- Are spreads described as variable, and what definition do they use for “spread” in their pricing documentation?
- Are there any additional charges that apply only under certain conditions (order types, account settings, or execution circumstances)?
A practical next question is whether the broker’s documents explain how execution quality and variability are handled in different market conditions, so you can treat realized cost as variable, not fixed.