Fill or kill, immediate or cancel: what the order flags do to a scalper
Posted: Sat Oct 31, 2026 8:16 pm
Order types go beyond market and limit. Execution flags control what happens to the part of an order that can't be filled right away.
Fill or kill means the whole order must fill immediately or be cancelled. Immediate or cancel fills whatever is available and cancels the rest. In MetaTrader, these appear as filling modes, and the choice depends on the broker and the instrument.
Picking the wrong mode causes rejections that look mysterious. An order sent with a fill-or-kill flag on a thin pair gets cancelled if the full size isn't available. One sent as return might leave a partial fill resting in the book.
For scalpers, immediate or cancel is often a practical choice, since a partial fill is usually better than none. For strategies that need exact size, fill or kill avoids partial positions at the cost of more rejections.
Checking the symbol's allowed filling modes in the specification avoids errors.
It is also worth noticing that filling modes can differ between symbols on the same account. A setting that works on EURUSD may be rejected on a cross, which is a classic reason an advisor behaves perfectly on one pair and fails on another.
Which filling mode do your orders use, and was it chosen on purpose?
Fill or kill means the whole order must fill immediately or be cancelled. Immediate or cancel fills whatever is available and cancels the rest. In MetaTrader, these appear as filling modes, and the choice depends on the broker and the instrument.
Picking the wrong mode causes rejections that look mysterious. An order sent with a fill-or-kill flag on a thin pair gets cancelled if the full size isn't available. One sent as return might leave a partial fill resting in the book.
For scalpers, immediate or cancel is often a practical choice, since a partial fill is usually better than none. For strategies that need exact size, fill or kill avoids partial positions at the cost of more rejections.
Checking the symbol's allowed filling modes in the specification avoids errors.
It is also worth noticing that filling modes can differ between symbols on the same account. A setting that works on EURUSD may be rejected on a cross, which is a classic reason an advisor behaves perfectly on one pair and fails on another.
Which filling mode do your orders use, and was it chosen on purpose?