How to build a prop firm-compliant EA for MT5 — complete guide

What prop firm rules actually mean in MQL5 code

Proprietary trading firms enforce strict quantitative rules designed to test risk management. In MQL5, compliance is not merely about setting stop losses—it requires active equity tracking, high-water mark calculations, and automated execution halts. - **Daily Drawdown Limit**: Calculated from the starting balance/equity of the trading day (typically 00:00 server time). - **Maximum Total Loss**: Hard equity limit based on initial account size. - **Trailing Equity Stop**: High-water mark trailing loss threshold that moves up as profit grows.

Daily drawdown, max loss and trailing equity stops — how to implement each

1. Daily Drawdown Engine

The daily drawdown monitor captures equity at midnight server time and halts trading if loss threshold is breached: ``mql5 //+------------------------------------------------------------------+ //| Daily Drawdown Verification | //+------------------------------------------------------------------+ datetime lastReset; double startOfDayEquity; void CheckDailyDrawdown(double maxDailyLossPct) { MqlDateTime dt; TimeToStruct(TimeCurrent(), dt); if(dt.hour == 0 && dt.min == 0 && dt.day != lastReset) { startOfDayEquity = AccountInfoDouble(ACCOUNT_EQUITY); lastReset = dt.day; } double currentEquity = AccountInfoDouble(ACCOUNT_EQUITY); double maxLossAllowed = startOfDayEquity * (maxDailyLossPct / 100.0); if(startOfDayEquity - currentEquity >= maxLossAllowed) { CloseAllPositions(); GlobalVariableSet("EA_HALT_TODAY", 1); } } `

2. Trailing Equity Stops

Relative trailing drawdown tracks maximum account equity and locks in hard stops: `mql5 double highWaterMark = 0; void CheckTrailingEquityStop(double maxTrailingDrawdownPct) { double currentEquity = AccountInfoDouble(ACCOUNT_EQUITY); if(currentEquity > highWaterMark) { highWaterMark = currentEquity; } double maxAllowedLoss = highWaterMark * (maxTrailingDrawdownPct / 100.0); if((highWaterMark - currentEquity) >= maxAllowedLoss) { CloseAllPositions(); ExpertRemove(); // Emergency removal to halt trading } } ``

News filter logic

High-impact economic news releases create slippage and spread spikes. Implementing a news filter involves querying an economic calendar API or reading an embedded news CSV file to halt entry orders 15 minutes before and after high-impact events.

Testing your EA against prop firm conditions before submission

Standard MetaTrader backtesting does not capture variable spreads or tick-level slippage. Before submitting to a prop firm: - Run backtests with **every tick based on real ticks**. - Simulate **stress spreads** (e.g., 50-100 points during rollover). - Perform **walk-forward optimization** across multiple market regimes.

Common mistakes that get EAs flagged

1. **Grid & Martingale Logic**: Most prop firms use automated detectors that flag doubling lot sizes after losses. 2. **Trade Copying Collusion**: Using identical magic numbers, lot sizing, and entry timestamps across multiple client accounts. 3. **Rollover Execution**: Opening orders during 23:59-00:05 server rollover when liquidity thins out and spreads widen by 10x.