OrderSend Error 129 in MT4/MQL4: Invalid Price Fix

OrderSend Error 129 in MT4/MQL4 means that the price passed to OrderSend() is invalid. The MQL4 error name is ERR_INVALID_PRICE.

For market orders, one of the first things to check is whether the EA is using the correct current price: Ask for Buy and Bid for Sell. Price precision and the timing of the price update should also be checked.

What Does OrderSend Error 129 Mean?

• Error code: 129
• Error name: ERR_INVALID_PRICE
• Meaning: Invalid price

Error 129 means that MT4 did not accept the price supplied in the trade request.

The relevant argument is the price parameter in OrderSend().

int ticket = OrderSend(
    Symbol(),
    OP_BUY,
    Lots,
    price,
    Slippage,
    StopLoss,
    TakeProfit,
    "buy order",
    Magic,
    0,
    clrBlue
);

If price is not valid for the order being sent, OrderSend() returns -1. You can then read the MQL4 error code with GetLastError().

Common Causes of OrderSend Error 129

Use Ask for Buy and Bid for Sell

For MT4 market orders, Buy and Sell orders use different sides of the quote.

Buy Order Example

RefreshRates();

double price = NormalizeDouble(Ask, Digits);

ResetLastError();

int ticket = OrderSend(
    Symbol(),
    OP_BUY,
    Lots,
    price,
    Slippage,
    0,
    0,
    "buy order",
    Magic,
    0,
    clrBlue
);

if(ticket < 0)
{
    int err = GetLastError();

    Print("OrderSend failed. Error=", err,
          " Ask=", Ask,
          " Price=", price);
}

Sell Order Example

RefreshRates();

double price = NormalizeDouble(Bid, Digits);

ResetLastError();

int ticket = OrderSend(
    Symbol(),
    OP_SELL,
    Lots,
    price,
    Slippage,
    0,
    0,
    "sell order",
    Magic,
    0,
    clrRed
);

if(ticket < 0)
{
    int err = GetLastError();

    Print("OrderSend failed. Error=", err,
          " Bid=", Bid,
          " Price=", price);
}

Call RefreshRates Before Reading the Execution Price

An EA may perform indicator calculations, loops, file processing, or other work before it reaches OrderSend(). During that time, the market price may change.

Calling RefreshRates() immediately before reading Bid or Ask helps update the predefined price variables available to the EA.

RefreshRates();

double buyPrice =
    NormalizeDouble(Ask, Digits);

double sellPrice =
    NormalizeDouble(Bid, Digits);

It is better to calculate the execution price immediately before sending the order rather than storing a market price much earlier in the EA logic.

Normalize the Order Price

A calculated price may contain more decimal precision than the symbol supports. Before passing a calculated price to a trade function, normalize it to the symbol’s number of digits.

double price =
    NormalizeDouble(Ask, Digits);

The same principle applies to calculated stop-loss, take-profit, and pending-order prices.

RefreshRates();

double price =
    NormalizeDouble(Ask, Digits);

double sl =
    NormalizeDouble(Ask - 100 * Point, Digits);

double tp =
    NormalizeDouble(Ask + 100 * Point, Digits);

Pending Order Prices Need Two Checks

Pending orders need more than a normalized price. You should check both:

1. The price is on the correct side of the current market.
2. The price satisfies the broker’s minimum distance requirements.

A simple direction check can be written like this:

bool IsPendingPriceDirectionValid(int orderType, double price)
{
    RefreshRates();

    price = NormalizeDouble(price, Digits);

    if(orderType == OP_BUYLIMIT)
        return price < Ask;

    if(orderType == OP_BUYSTOP)
        return price > Ask;

    if(orderType == OP_SELLLIMIT)
        return price > Bid;

    if(orderType == OP_SELLSTOP)
        return price < Bid;

    return false;
}

MQL4 Helper Function for Market Order Prices

If the EA opens both Buy and Sell positions, a small helper function can keep the price-selection rule in one place.

double GetMarketOrderPrice(int orderType)
{
    RefreshRates();

    if(orderType == OP_BUY)
        return NormalizeDouble(Ask, Digits);

    if(orderType == OP_SELL)
        return NormalizeDouble(Bid, Digits);

    return 0;
}

Example:

int orderType = OP_BUY;

double price =
    GetMarketOrderPrice(orderType);

if(price <= 0)
{
    Print("Unsupported order type.");
    return;
}

ResetLastError();

int ticket = OrderSend(
    Symbol(),
    orderType,
    Lots,
    price,
    Slippage,
    0,
    0,
    "market order",
    Magic,
    0,
    clrBlue
);

if(ticket < 0)
{
    int err = GetLastError();

    Print("OrderSend failed. Error=", err,
          " Price=", price,
          " Bid=", Bid,
          " Ask=", Ask);
}

For a larger EA, the same idea can be expanded into a reusable wrapper that also handles lot validation, spread checks, retries, and error logging.

How to Debug OrderSend Error 129

When Error 129 occurs, do not only print the error number. Print the values that were actually used to build the order request.

RefreshRates();

Print("OrderType=", orderType);
Print("Bid=", Bid);
Print("Ask=", Ask);
Print("Price=", price);
Print("Digits=", Digits);
Print("Point=", Point);
Print("NormalizedPrice=",
      NormalizeDouble(price, Digits));

Then check the Experts and Journal tabs in MT4.

A practical debugging order is:

1. Confirm the exact error is 129.
2. Confirm the order symbol.
3. Confirm Buy uses Ask and Sell uses Bid.
4. Call RefreshRates().
5. Normalize the execution price.
6. For pending orders, check direction and minimum distance separately.
7. Print the exact values sent to OrderSend().

Error 129 vs Error 130 vs Error 138

These three errors can appear during order execution, but they indicate different problems.

If MT4 returns 129, investigate the actual execution price first. If it returns 130, investigate stop and pending-order distances. If it returns 138, refresh the market price and review the execution/retry logic.

Related OrderSend Errors

Related MQL4 OrderSend Guides

FAQ About OrderSend Error 129

Summary

OrderSend Error 129 in MT4/MQL4 is ERR_INVALID_PRICE. The fastest way to debug it is to inspect the exact price that the EA passed to OrderSend().

• Error 129 means Invalid Price.
• Use Ask for Buy market orders.
• Use Bid for Sell market orders.
• Call RefreshRates() before calculating a fresh execution price when needed.
• Normalize calculated prices with NormalizeDouble(price, Digits).
• For pending orders, check both price direction and minimum stop distance.
• Do not confuse Error 129 with Error 130 or Error 138.
• Use GetLastError() immediately after a failed OrderSend() call.

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