Execution Quality · 7 min read
Slippage occurs when an order fills at a different price than requested. In fast-moving markets, the price you saw when the EA generated the signal can differ from the price at which the broker actually fills the order — sometimes by a fraction of a pip, sometimes by several pips during news events.
For EAs running hundreds of trades per year, slippage is a systematic cost that compounds into real money. Understanding why it happens and how to minimize it is part of running a professionally managed automated system.
Why Slippage Happens
Three main causes:
- Latency: Time passes between when the EA generates a signal and when the order reaches the broker’s server. During that time, price can move. Lower VPS latency reduces this gap.
- Low liquidity: When market liquidity is thin (news events, holiday periods, early Asian session), orders cannot always fill at the requested price because insufficient counterparty volume exists at that level.
- Market impact: Large orders can move the price. At EA lot sizes (0.01-0.1 lots), this is rarely an issue for retail traders — but larger institutional-scale automated systems face this routinely.
Slippage’s Impact on EA Performance
For H1 martingale EAs with large take-profit targets (15-30 pips), slippage of 0.5-1.0 pip per trade is a manageable percentage of the total expected move. The same slippage on a scalping EA targeting 3-5 pips per trade is catastrophic — 0.5 pip slippage is 10-17% of the expected profit per trade.
This is one reason H1 strategies are more robust to real-world execution conditions than M1-M5 strategies: the larger expected move per trade means execution imperfection is a smaller percentage of the total.
How to Minimize Slippage
1. Choose a Low-Latency VPS Near Your Broker
The single most impactful change. A VPS in the same Equinix data center as your broker can achieve 1-2ms execution latency versus 100-300ms from a geographically distant VPS. This eliminates most latency-based slippage.
2. Use an ECN/STP Broker
ECN brokers pass orders directly to the interbank market, where deep liquidity pools minimize the gap between requested and filled price. Market makers fill from their own book and have more discretion over fill prices.
3. Avoid Trading Through High-Risk News Events
Slippage spikes during NFP, FOMC, and other major releases when price moves too fast for limit orders to fill cleanly. News filters prevent EA entries during these windows — reducing slippage exposure along with news risk.
4. Include Realistic Slippage in Backtests
MetaTrader’s Strategy Tester has a slippage setting. Use 2-5 points of slippage in your backtests (0.2-0.5 pips). If the system remains profitable at this slippage level, it has demonstrated robustness to real-world execution conditions.
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