The costs toggle is the simulation assumption that decides whether a backtest's results include trading costs and financing, or are shown gross of them. In the app it is the switch labelled Costs & interests, described as "Trading costs, financing & interest" and shortened to "Costs" in the assumptions summary. It changes what the same run is showing, not the strategy itself.
Also seen as: Costs & interests, Costs
What does turning costs on change?
Turning Costs & interests on deducts every modelled cost of trading and financing from the run you are looking at. Three components get wired in:
- Transaction cost — a flat fee charged once per trade execution.
- Slippage — a proportional cost on each fill, for the gap between the quoted and the filled price.
- Interest-rate markups — the financing cost of borrowing for leverage or for shorting, charged as a spread over a reference rate. The same switch turns on the interest credited to idle cash — see interest received and paid.
With the toggle off, all three are zero: the results assume trading and financing were free.
How does Fincanva handle it?
- Trading costs are not included on the Free plan. On Free the assumption stays off and the toggle cannot be turned on, so a Free backtest is always a costless one; Starter, Advanced, Ultimate and Professional all include it. See what each plan includes.
- Costs & interests is off by default, so the figures you meet first are gross of costs and financing.
- Flipping it switches the displayed result immediately, with no new run — every combination is pre-computed when the strategy runs (see simulation assumptions).
- It moves every number derived from the equity curve, not only the cost lines: total return, annualized return, the monthly figures and the risk metrics all change.
- What it deducts shows up as its own bands in the P&L breakdown — "Costs" and "Interest paid".
- The two interest-rate markups are saved settings you can edit, separate from the toggle that switches them in or out; the per-trade fee and the slippage fraction are fixed platform assumptions with no setting in the app.
- The Positions view does not follow this toggle: it always reports with costs off, one of its Positions forced assumptions.
What does it look like in practice?
One run, viewed twice. With Costs & interests off the run shows a total return of +42.0%. Flip it on and the same run shows +38.6%: the 3.4pp difference is the trading fees, slippage and financing the strategy would have paid over the period. Nothing about the strategy changed and no new backtest ran — you switched from the gross view to the after-cost view of the identical run. How wide the gap is depends on how much the strategy trades: one that rebalances monthly pays the per-trade fee far more often than one that holds for years.
The figures on this page describe what Fincanva models, not what you should do with your money — see Is this financial advice?.