MT5 is not just MT4 with a new coat of paint
Posted: Sat Oct 31, 2026 6:43 pm
Treating MT4 and MT5 as interchangeable is the quickest way to get surprised by order handling. Two differences cause most of the trouble.
First, account type. MT4 is hedging by default, so every order is its own ticket. MT5 accounts come as either netting or hedging, depending on what the broker enables. On a netting account, a second buy on the same symbol merges into the existing position. The entry becomes an average, and the stop and target of the position get rewritten by whatever was set last. A scalper who scales in and out suddenly finds one position where there used to be three tickets.
Second, filling modes. MT5 lets each symbol allow different policies, such as fill or kill, immediate or cancel, and return. A script or EA ported from MT4 without checking which mode the symbol accepts can get rejections with a vague error that looks like a connection problem but is not.
Blunt opinion: check the account type and the allowed filling modes before looking at anything else, because those two explain more oddities than spreads or latency do.
On which brokers have you found the MT5 filling mode setting causing rejections, and how did you spot it?
First, account type. MT4 is hedging by default, so every order is its own ticket. MT5 accounts come as either netting or hedging, depending on what the broker enables. On a netting account, a second buy on the same symbol merges into the existing position. The entry becomes an average, and the stop and target of the position get rewritten by whatever was set last. A scalper who scales in and out suddenly finds one position where there used to be three tickets.
Second, filling modes. MT5 lets each symbol allow different policies, such as fill or kill, immediate or cancel, and return. A script or EA ported from MT4 without checking which mode the symbol accepts can get rejections with a vague error that looks like a connection problem but is not.
Blunt opinion: check the account type and the allowed filling modes before looking at anything else, because those two explain more oddities than spreads or latency do.
On which brokers have you found the MT5 filling mode setting causing rejections, and how did you spot it?