Active rules pay a bill the signal does not show

strategyPublished 20 October 20261 min readmulti asset

Key points

• Turnover multiplies a per-trade cost.
• A cost already inside the fill should not be added again as a separate spread.
• Financing applies when the position is held, on terms you have to read. This note does not quote a rate.

What is going on

Each round trip can pay a commission and cross a spread. Slippage is the further gap when the fill is worse than the decision price. A strategy that trades often pays that stack often. One that holds overnight on a contract with financing pays a carrying charge that a same-day round trip does not. The commission research on this site separates explicit charges from an implicit spread so they are not counted twice. The same discipline applies to a trading rule.

Why it matters

A backtest that fills at the signal price with no spread has described a different strategy from the one you can trade. Market impact grows with size. A stop that gaps is a larger cost than the worksheet. Borrowing to hold the position, where the product allows it, adds a charge that rises with the holding period. None of these appears in a chart that only marks entries and exits.

What to watch

Count the turns in the rule you actually intend to run. Write a spread and a slippage figure you are willing to assume, and say they are assumptions. Read whether the product charges financing. Compare the distance of the planned trade with that stack before calling the rule attractive.

Risks

A quiet spread is a poor guide to the spread on the day you need to leave. This page does not publish a strategy’s historical cost or a live tariff.