Time in force

A parameter of an order, separate from its type and its price. The order type says what price the order may be filled at; the time in force says how long the attempt lasts. The common values are settled across the industry: good for day, which expires at the end of the trading day; good til cancelled, which rests until it fills or is removed; good til date, which rests until a stated date and time; immediate or cancel, which fills whatever is available at once and cancels the remainder; and fill or kill, which fills the whole order at once or cancels all of it.

The distinction that matters most is between the two that permit a partial fill and the one that does not. Immediate or cancel accepts whatever quantity is resting and abandons the rest, which leaves a position smaller than the one requested. Fill or kill refuses that outcome and leaves no position at all. Both are answers to the same problem of thin depth, and they fail in opposite directions.

The frequent misreading is that good til cancelled means forever. It does not. Venues and firms apply their own expiry conventions, orders are commonly cleared at a defined horizon or at a contract's expiry, and a corporate action on a share can cause resting orders to be removed. A resting order also remains an instruction rather than a reservation: it holds no place in a queue at a price the market has not reached, and in a fast market it can be passed over entirely.