MetaTrader Common Errors: MT4 and MT5 Codes, Causes and Server-Side Fixes

How MetaTrader reports errors

MetaTrader reports errors as numbered codes with fixed names that MetaQuotes documents, and the number tells you where in the chain the request failed. MT4 and MT5 use different numbering, so the same problem has two different codes depending on the platform.

In MetaTrader 5, every trade request gets a reply from the trade server. MetaQuotes describes the mechanism like this:

"All requests to execute trade operations are sent as a structure of a trade request MqlTradeRequest using function OrderSend(). The function execution result is placed to structure MqlTradeResult, whose retcode field contains the trade server return code."— MQL5 Reference, Trade Server Return Codes, MetaQuotes (accessed October 2026)

MT5 trade server return codes run from 10004 (TRADE_RETCODE_REQUOTE) to 10046 (TRADE_RETCODE_HEDGE_PROHIBITED). In MetaTrader 4, the same kind of information comes from GetLastError(). Trade-related codes sit in the low range (0–150, for example 130 ERR_INVALID_STOPS). Program runtime errors start at 4000 (for example 4109 ERR_TRADE_NOT_ALLOWED).

A success code is not the same as a filled order. The MQL5 reference for OrderSend() warns that "a successful result of the OrderSend() function does not mean that the order has been executed". It only means the request was accepted for further processing. When a client says "it said OK but nothing happened", check the server journal.

There are three places to look for the real code:

• Journal tab (platform events: connection, login, order requests).
• Experts tab (messages printed by Expert Advisors and scripts, including GetLastError() results).
• Log files on disk. MetaQuotes' MT5 help states: "The platform log files are stored in the Logs directory, and Expert log files are saved in MQL5\Logs. File names correspond to the date of journal generation — YYYYMMDD.LOG."

The built-in log viewer can filter entries by "Full, No connection, Errors only".

Connection errors: "No connection" and "Invalid account"

"No connection" means the terminal cannot reach the trade server address it was given, and "Invalid account" means it reached a server that rejected the login. Each needs different checks, and the broker can see things the trader cannot.

What the trader can check

1. Confirm the internet connection works in a browser.
2. Re-enter the login, the password and the exact server name. MT5 help notes that you can also type the address manually as "[server number]:[port number], for example, 192.168.0.1:443".
3. Check that the password is the master password. MetaQuotes explains that "Investor authorization allows you to see the account status, analyze prices, and work with your own Expert Advisors, but not trade."
4. Check the proxy and firewall. In MT5, the Server tab under Tools > Options holds the "setup of server connection, configuration of a proxy server".
5. Open the log viewer, filter by "No connection" and send the YYYYMMDD.LOG file to the broker.

What the broker should check on the server side

• Reachability of every access point. Test each address and port published in the server list from outside your own network, and test from more than one region.
• Recent infrastructure changes. New IPs, DNS records, data-centre moves or DDoS-protection rules often cause "No connection" waves.
• Server health. CPU, memory and disk on the trade and access servers. Overload shows up as timeouts (128 ERR_TRADE_TIMEOUT, 10012 TRADE_RETCODE_TIMEOUT) before full disconnects.
• Account state. Is the account enabled? Is it in the right group? Was it moved during a migration? Was a forced password change switched on? MT5 help confirms that "Forced password change can be enabled by the trade server administrator."
• Old client builds. 5 ERR_OLD_VERSION ("Old version of the client terminal") means the terminal needs updating.

For deeper network and host issues, see forex server troubleshooting and MetaTrader server hosting.

MT4 error codes and their MT5 equivalents

MT4 trade errors use small numbers that MetaQuotes lists in the MQL4 Reference, and most have a direct MT5 counterpart. Use the mapping below when clients move between platforms or when you run both servers during an MT4 to MT5 migration.

The mapping is our practical guide, not an official MetaQuotes table. The descriptions themselves are quoted from the MQL4 Trade Server Return Codes page.

Trade context busy (146) is MT4-specific. The MQL4 function IsTradeContextBusy() "returns true if a thread for trading is occupied by another Expert Advisor". It is a client-side issue. Several EAs in one terminal are competing for the trading thread, and the fix is retry logic or fewer EAs per terminal. The broker cannot fix it on the server.

Autotrading and permission errors

Autotrading errors split cleanly by name: 10026 says the server disabled it, and 10027 says the client terminal did. In MT4, the client-side equivalent is runtime error 4109.

Plugins can also block or rewrite requests. A risk or routing plugin that rejects orders shows up to the client as a generic rejection (10006) or common error (2). If rejections started after a plugin update, check that plugin first. We build and maintain these as part of MetaTrader plugin development.

From firefighting to monitoring

Most recurring MetaTrader errors can be detected in the server logs before clients complain. You get there by watching error rates instead of single tickets. A rise in 10021 on one symbol, timeouts during one session, or rejects after a bridge restart are all visible in logs minutes after they start.

FXSUPPORT provides MT4/MT5 platform support for brokers and prop firms: setup, updates, backups, configuration, log monitoring and bridge configuration. We also cover server infrastructure in the UK and the Netherlands with monitoring and a 99.9% uptime target. In practice, that means we:

• watch platform and bridge logs for error patterns, not only outages;
• review symbol, session and group settings after every change and before DST switches;
• check plugin behaviour after platform updates;
• harden servers against DDoS and keep backups restorable.

If you run a brokerage and your support team spends its days answering the same error tickets, that is a sign the cause sits on the server. See MT5 support and MT4 support for what we cover, or contact us for a free technical review.