MT4 error 131: Invalid trade volume

What MQL4 says

131 ERR_INVALID_TRADE_VOLUME

Invalid trade volume

From MQL4's table of error codes, read 24 October 2026. An Expert Advisor reads it with GetLastError() after a call fails; the Experts and Journal tabs print what the EA logs.

What causes it

The lots passed to OrderSend() are a volume the symbol doesn't take. MarketInfo() gives the symbol's limits: MODE_MINLOT (minimum permitted amount of a lot), MODE_MAXLOT (maximum permitted amount of a lot) and MODE_LOTSTEP (step for changing lots).

Position size calculator: lots from your risk and stop

How to fix it

Send a lot size the symbol accepts. Round the lots down to a multiple of MODE_LOTSTEP and keep them between MODE_MINLOT and MODE_MAXLOT, read from MarketInfo() for the symbol you trade instead of hard-coded; if the rounded lots fall under MODE_MINLOT, skip the trade.

Source: MQL4 Reference: MarketInfo identifiers. No MQL4 code is shown because none here was compiled; adapt the steps to your EA.

The same error in MT5

MT5 returns it as a trade server code instead: MT5 error 10014: Invalid volume in the request.

Other MT4 errors

• MT4 error 0: No error returned
• MT4 error 1: No error returned, but the result is unknown
• MT4 error 2: Common error
• MT4 error 3: Invalid trade parameters
• MT4 error 130: Invalid stops
• MT4 error 132: Market is closed
• MT4 error 133: Trade is disabled
• MT4 error 134: Not enough money
• MT4 error 136: Off quotes
• MT4 error 4051: Invalid function parameter value
• MT4 error 4107: Invalid price
• MT4 error 4111: Shorts are not allowed
• MT4 error 4112: Automated trading by Expert Advisors/Scripts disabled by trade server
• MT4 error 4200: Object already exists
• MT4 error 5004: Cannot open file