Stop-Limit Order

Stop-limit orders extend the basic stop-loss concept by adding a fill-price constraint. Where a standard stop-loss becomes a market order on trigger (filling at the best available price, potentially with significant slippage during fast markets), a stop-limit becomes a limit order on trigger (filling only at the limit price or better).

Mechanics: 1. Place stop-limit with stop price S and limit price L 2. Order remains pending while price is on the safe side of S 3. When market reaches S, the order activates as a limit order at price L 4. Order fills only if price is at L or better; if price moves past L without filling, the order remains pending (or expires per time-in-force)

For a buy stop-limit: stop S above current price, limit L typically slightly above S. Buy executes only when price reaches S AND can be filled at or below L.

For a sell stop-limit: stop S below current price, limit L typically slightly below S. Sell executes only when price reaches S AND can be filled at or above L.

Use cases in forex EAs:

1. Breakout entry with slippage protection: instead of a buy-stop at the breakout level (which fills at any price during fast breakout, often with 5-15 pip slippage), use a buy-stop-limit with stop at breakout level and limit at breakout + 3 pips. The EA accepts up to 3 pips slippage but rejects fills beyond that. Trade-off: may miss the fastest breakouts entirely.

2. Stop-loss with slippage cap (rare in retail forex): instead of a market stop-loss that may execute 10-20 pips below the stop level during a gap, a stop-limit caps the loss at the limit but risks no fill — the position may run far past the limit if price gaps through. This is generally NOT recommended for stop-losses because the protection is the worst case scenario; risking no fill defeats the purpose.

3. Take-profit with floor: a sell stop-limit at the take-profit level with limit slightly below ensures the profit-taking exit doesn't execute at a price worse than the limit. Trade-off: may miss the exit entirely if price gaps below the limit.

MetaTrader support: MT5 supports stop-limit orders (`ORDER_TYPE_BUY_STOP_LIMIT` and `ORDER_TYPE_SELL_STOP_LIMIT`); MT4 does not natively support stop-limit, requiring EA-level emulation (monitor for stop trigger, then place limit order on activation).

When NOT to use stop-limit: standard stop-losses for position protection should use the regular stop-loss (market on trigger), not stop-limit. The whole point of a stop-loss is to guarantee the position exits when reached; risking no fill negates the protection.