MT5 error 4756: Trade request sending failed

What MQL5 says

4756 ERR_TRADE_SEND_FAILED

Trade request sending failed

From MQL5's table of runtime errors, read 24 October 2026. An Expert Advisor reads it with GetLastError() after a call fails; the Experts tab prints what the EA logs.

What causes it

OrderSend() returned false, and 4756 says no more than that. MQL5's OrderSend page says to read the result structure: its retcode is the trade server's own reason, one of the return codes on this site.

Look up the retcode the server sent

The fix in MQL5

Print the result's retcode (CTrade's ResultRetcode() and ResultRetcodeDescription()) and look that code up; check a request first with OrderCheck(), which answers with a return code without sending.

#include <Trade/Trade.mqh>
CTrade trade;

void OpenBuy(const double lots)
  {
   if(!trade.Buy(lots, _Symbol))
      Print("Buy failed: ", GetLastError());   // 4756 says only that sending failed
  }

#include <Trade/Trade.mqh>
CTrade trade;

void OpenBuy(const double lots)
  {
   if(!trade.Buy(lots, _Symbol))
      PrintFormat("Buy failed: retcode %u (%s)", trade.ResultRetcode(), trade.ResultRetcodeDescription());
  }

Both compile in MetaEditor 5 with no errors or warnings. Adapt them to your EA; they were not run against a trade server.

Other MT5 errors

• MT5 error 4014: Function is not allowed for call
• MT5 error 4753: Position not found
• MT5 error 4802: Indicator cannot be created
• MT5 error 4806: Requested data not found
• MT5 error 5004: File opening error
• MT5 error 10004: Requote
• MT5 error 10006: Request rejected
• MT5 retcode 10009: Request completed
• MT5 error 10013: Invalid request
• MT5 error 10014: Invalid volume in the request
• MT5 error 10015: Invalid price in the request
• MT5 error 10016: Invalid stops in the request
• MT5 error 10017: Trade is disabled
• MT5 error 10018: Market is closed
• MT5 error 10019: There is not enough money to complete the request
• MT5 error 10021: There are no quotes to process the request
• MT5 error 10022: Invalid order expiration date in the request
• MT5 error 10026: Autotrading disabled by server
• MT5 error 10027: Autotrading disabled by client terminal
• MT5 error 10030: Invalid order filling type
• MT5 error 10031: No connection with the trade server
• MT5 error 10044: The request is rejected, because the "Only position closing is allowed" rule is set for the symbol
• MT5 error 10046: The request is rejected, because the "Opposite positions on a single symbol are disabled" rule is set for the trading account.