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Understanding Slippage in Backtesting

Sachin Yadav

Your backtest may look profitable because it assumes perfect execution.

Historical charts often make entries and exits look cleaner than they are in live trading.

In reality, market orders can receive worse prices than expected, and stop orders may experience slippage during fast conditions.

A strategy that targets small movements can be particularly sensitive to transaction costs.

When testing an NQ setup, I want to include realistic commissions, fees, and slippage assumptions.

I also consider whether the historical data supports the execution assumptions I'm making.

A backtest should estimate how the strategy might behave under realistic conditions.

If the results disappear after reasonable trading costs, the apparent edge may not be robust enough.

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  • Prop Firm BridgeOfficial

    Slippage occurs when a market order or stop order executes at a different price than requested due to fast-moving markets or low liquidity. Especially on volatile instruments like NQ futures, ignoring commissions, fees, and realistic fill assumptions can make a losing strategy look profitable on paper.

    When trading with a prop firm, unmodeled slippage can quickly erode small profit margins and push you dangerously close to strict daily loss limits. Always factor in realistic transaction costs and test your historical data rigorously before deploying capital.

    We would love to hear from other traders in the community: how do you typically measure and adjust for slippage in your backtests?

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