MQL4 ERR_INVALID_PRICE
MQL4 error 129 invalid price maps to ERR_INVALID_PRICE: invalid price. OrderSend can return 129 when the requested price is invalid or not normalized for the symbol. Capture GetLastError immediately after the failed call, correct the cause, and retry only when the condition can change.
Open the Coding Agent, then choose MQL4 from the language menu.
#property strict
#property script_show_inputs
input double Lots = 0.10;
input int Slippage = 3;
void OnStart()
{
if(!IsTradeAllowed())
{
Print("Trading is not currently allowed or the trade context is busy.");
return;
}
RefreshRates();
double price = NormalizeDouble(Ask, Digits);
ResetLastError();
int ticket = OrderSend(Symbol(), OP_BUY, Lots, price, Slippage,
0, 0, "diagnostic", 0, 0, clrNONE);
if(ticket >= 0)
{
Print("Order opened. Ticket ", ticket);
return;
}
int error_code = GetLastError();
Print("OrderSend failed. error=", error_code,
" symbol=", Symbol(), " lots=", DoubleToString(Lots, 2),
" ask=", DoubleToString(price, Digits));
}The official MQL4 runtime table names error 129 ERR_INVALID_PRICE and defines it as “invalid price.” OrderSend can return 129 when the requested price is invalid or not normalized for the symbol.
The error number is evidence about one failed call, not a diagnosis of the whole EA. Read the API sentinel first, then call GetLastError immediately because that function returns the current _LastError value and resets it.
Start with the inputs and external state that existed at the failure point. A later log entry or a successful call can overwrite the useful context.
Rebuild the request from a fresh valid quote. Do not resend the rejected price unchanged.
Keep the original trading and risk rules intact. A workaround that widens stops, increases volume, changes an account setting, or ignores a failed return value can hide the symptom while changing the system.
| Check | Action |
|---|---|
| A buy does not use the current Ask or a sell does not use the current Bid | Use current Ask for buys and current Bid for sells on the active symbol. |
| The price belongs to another symbol or an old quote | Read prices for the exact order symbol and refresh before sending. |
| The price is not normalized to the symbol digits | Normalize the request price to the symbol digits and tick rules. |
| A pending-order price violates the requested order type | Validate pending-order direction and distance before OrderSend. |
The script refreshes rates, normalizes Ask, and logs the exact price passed to OrderSend. Multi-symbol code must obtain the quote and digits for the order symbol instead.
The example improves validation and logging. It does not prove the operation will be accepted by a broker or behave safely in live trading.
#property strict
#property script_show_inputs
input double Lots = 0.10;
input int Slippage = 3;
void OnStart()
{
if(!IsTradeAllowed())
{
Print("Trading is not currently allowed or the trade context is busy.");
return;
}
RefreshRates();
double price = NormalizeDouble(Ask, Digits);
ResetLastError();
int ticket = OrderSend(Symbol(), OP_BUY, Lots, price, Slippage,
0, 0, "diagnostic", 0, 0, clrNONE);
if(ticket >= 0)
{
Print("Order opened. Ticket ", ticket);
return;
}
int error_code = GetLastError();
Print("OrderSend failed. error=", error_code,
" symbol=", Symbol(), " lots=", DoubleToString(Lots, 2),
" ask=", DoubleToString(price, Digits));
}Pineify can generate or revise one self-contained .mq4 file with MQL4-specific reference context. Its independent static checker returns MetaEditor diagnostics so you can repair source issues before testing in your own MT4 environment.
Open MQL4 Coding AgentStatic diagnostics do not prove runtime behavior, backtest results, broker compatibility, or live-trading safety.
Check the API return value before interpreting an error number from the log.
Call GetLastError immediately and record error 129, symbol, prices, volume, ticket, and terminal state relevant to the operation.
Use current Ask for buys and current Bid for sells on the active symbol.
Compile the revised source, then test with the same MT4 build, broker, symbol, account permissions, and market state.
ERR_INVALID_PRICE means invalid price. The code should still identify which API returned failure and log the inputs used for that call.
A buy does not use the current Ask or a sell does not use the current Bid The price belongs to another symbol or an old quote The price is not normalized to the symbol digits A pending-order price violates the requested order type
Rebuild the request from a fresh valid quote. Do not resend the rejected price unchanged.
It reports the current _LastError value and resets it. Other operations can change the error state, so a delayed read may describe the wrong call.
Pineify can revise a self-contained .mq4 file, add validation and error logging, and return static MetaEditor diagnostics. It cannot prove broker acceptance, account permissions, market availability, or live execution.
Last verified against the linked official references on . Compile and test the final source in the MetaTrader 4 build, broker, symbol, and account environment you plan to use.
Define the requirement, inspect the generated source, repair diagnostics, and test the behavior in your own MT4 environment.
Open Coding Agent