Direct and indirect costs that can affect STP trading
“Costs” in forex usually mean more than one number. The most visible items are charged directly, such as spreads or commissions. Other items can arise indirectly from how orders are executed, how fast they are filled, and what charges apply to holding positions. In STP (Straight Through Processing) models, the idea is often that client orders are sent for execution rather than being kept as an internal position; however, realized costs still depend on market conditions and the complete execution path.
In practice, you can group potential cost drivers into two categories:
- Direct costs: charges shown on pricing or statements (spreads, commissions, financing/holding charges, and certain transaction fees).
- Indirect costs: outcomes that change the effective entry/exit price or the total cost over time (slippage from price movement, execution timing, and external taxes or levies if applicable).
Mechanics: what “STP” changes about cost drivers
A useful way to think about STP is as a pipeline for order execution: your order is placed, it interacts with available liquidity, and it results in a fill (or partial fills). Even without assuming a specific broker, the following mechanics are common to execution-based costs:
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Price formation and spreads: The spread is the quoted difference between buy and sell prices at a given moment. In fast markets, the spread can widen, changing the cost of entering and exiting.
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Order routing and liquidity availability: If liquidity is thin or prices move quickly, the fill you receive may be worse than the last quote you saw. This shows up as slippage (a difference between expected and realized price).
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Time in market: Holding charges (often called financing or swap/rollover concepts) accumulate when positions remain open. The timing and terms determine how those charges affect total cost.
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Execution quality: Partial fills and delays can also increase effective cost, because you may exit different portions at different prices.
Evidence and examples you can verify independently
Because “STP broker” implementations vary, focus on verifiable components in your own records. Here are simple, testable examples and checks you can do without relying on promises.
Example 1: Spread and commission
Assumptions (so the math is clear):
- You buy and later sell the same instrument.
- Total cost comes from half-spread on entry plus half-spread on exit, plus any commission.
How to verify:
- Compare the quoted bid/ask around your order time to estimate the spread-based component.
- Check your account statement or trade confirmation for commissions or per-trade fees.
Example 2: Slippage around execution
Assumptions:
- You submit a market order (execution price may vary).
- Prices can move between the quote you see and the fill you receive.
How to verify:
- Record the displayed price when you placed the order.
- Compare it to the actual fill price(s) shown on confirmations.
- If fills repeatedly differ during similar volatility, slippage is a material factor.
Example 3: Financing or holding charges
Assumptions:
- You keep positions open over the period that triggers financing calculations.
How to verify:
- Look at the line items labeled as holding/financing/rollover (naming varies) on your statement.
- Confirm the date/time basis used for applying those charges.
Limitations and failure modes to watch for
Several limitations can prevent you from attributing all cost differences to “STP” alone:
- STP definitions can differ: The label may describe an execution philosophy, but it does not automatically guarantee identical pricing or execution quality.
- Market conditions dominate: When liquidity is limited or volatility rises, slippage and spread widening can overwhelm small differences in commission.
- Partial fills complicate comparisons: If one trade fills in multiple parts, the effective cost depends on the weighted average fill.
- Hidden or external charges: Some costs may appear outside a broker’s “commission” line, such as certain taxes or regulatory-related charges, depending on jurisdiction and product structure.
A material failure mode is assuming that a single advertised feature fully explains total cost. Total cost is the combined effect of quotes, execution, and holding charges.
Verification checklist and next question
To verify what costs affect you in an STP setup, use a paper-trail approach: