Spread, slippage and commission: the costs that quietly decide a backtest
How trading costs eat into profit, which strategies suffer most, and how to check a backtest includes them properly.
Every trade pays something: the spread between buy and sell prices, slippage when the fill is worse than the price you saw, and on some accounts commission and overnight swap. A backtest that leaves these out is describing a market that does not exist.
Who pays the most
- Strategies that trade very often.
- Strategies that aim for small moves, where the spread is a big share of each target.
- Strategies that trade at news or at the market open, when spreads widen and fills slip.
How to check a backtest
- Was it run on real tick data with real bid and ask prices, or on one price per minute?
- Does it add slippage on stop orders?
- Does it match the account type you will use?
The Arrissa REX 9 AI backtest replays real Exness bid and ask ticks, so the spread at every moment is already inside the result, including the wider spreads around the open.
Start the bot, watch your free $10,000 demo trade, and connect your Exness account when you are ready.
Read next: Why compounding makes every backtest look amazing
Risk warning. Trading leveraged products such as CFDs carries a high risk of losing money. Backtest figures are simulations, not real results, and past performance does not guarantee future results. Read the risk disclosure before you connect an account. Nothing here is financial advice.