Slippage
Definition
Slippage occurs when a trade is executed at a different price than expected. It happens during periods of high volatility or low liquidity, especially during news events. Slippage can be positive (better price) or negative (worse price). Using limit orders instead of market orders can help reduce slippage.
Further reading: Slippage
Slippage is the difference between the price an order is expected to fill at and the actual executed price. In forex automated trading this can be positive (better price) or negative (worse price) and is driven by latency, low liquidity, rapid price moves, or order type. For example, an EA that sends a market buy for EUR/USD expected at 1.2000 but is filled at 1.2003 experiences 0.0003 (3 pips) negative slippage. Stop orders, market orders and fills during news releases or market open/close are most vulnerable. Slippage also includes partial fills and gaps where an order executes across multiple price levels. Traders and developers should measure, log and set tolerances for slippage rather than assuming theoretical entry prices during strategy design.
Slippage appears at the moment of order execution and is most visible during high volatility, low liquidity, or slow routing. It affects live trading differently than historical backtests because real-world latencies, broker order-books and counterparty behavior change execution quality. Retail market makers, ECNs and STP brokers may each produce different slippage patterns; ECNs often show faster fills but still can gap on news. Slippage can also occur when orders trigger at stop levels and the next available price is beyond the stop. It is a practical consideration for risk calculation, position sizing and realistic performance reporting. Monitoring slippage by instrument, time of day and news events helps identify problem periods to avoid or adapt to.
Traders and EA developers use slippage controls to reduce execution surprises. Common techniques include setting a maximum slippage/tolerance parameter in the EA that cancels orders if execution exceeds the threshold, preferring limit or post-only orders when possible, and using smart order routing or aggregation across liquidity providers. EAs can log slippage statistics for each trade to refine parameters during optimization and disable trading during scheduled volatile events. Example: set max slippage = 3 pips for EUR/USD and cancel market order if fill price differs. Regular monitoring and adaptive thresholds let EAs balance fill speed against execution quality without promising profits.