Order Duration and Time in Force

Scope. This article explains the duration instructions attached to an order and what each one does. No duration is recommended and no order type is recommended for any situation. MarketClue accepts, routes and executes nothing. Prices are small non-canonical illustrative figures describing no actual security. Durations available and their handling vary by broker and venue — the descriptions below are the common conventions, not universal rules, and the specifics belong to an account agreement. United States market structure, checked 17 August 2026.

Duration determines how long an instruction stays alive, which determines what information it will eventually be executed against. That second consequence is the interesting one and almost nobody thinks about it.

The common designations

Day. Valid for the current session and cancelled at its end if unfilled. The most common default.

Good till cancelled. Persists across sessions until filled or cancelled. In practice brokers impose a maximum life, and the length varies between firms — so "till cancelled" generally means "till cancelled or until the firm's limit expires, whichever comes first."

Good till date. Persists until a stated date, then cancels.

Immediate or cancel. Fill whatever quantity is available right now; cancel the rest. Partial fills are the expected outcome rather than an exception.

Fill or kill. Fill the entire quantity immediately or cancel the whole order. No partial fill is possible.

At the open and at the close. Participate in the opening or closing auction rather than in continuous trading — a different mechanism, with its price set by the auction rather than by the book.

Extended-hours designations. Permit an order to work outside regular trading hours, which is a materially different environment and is dealt with below.

The property of resting orders that matters most

An order that persists is a standing commitment made with old information.

A good-till-cancelled order placed three weeks ago reflects what its author believed three weeks ago. It will execute on whatever happens today — an earnings release, a sector move, an announcement — and it has no capacity to know that anything changed. The instruction does not age; the reasoning behind it does.

The practical consequence is that a resting order is most likely to execute precisely when something has happened, because that is when prices move far enough to reach it. This is the same structural point as the adverse selection in Limit Orders, extended over time rather than across counterparties: the order fills when the world has changed, and it was written before the change.

Two mechanical hazards worth knowing

Corporate actions. A resting order that survives a split, a consolidation or a distribution may be adjusted, or may be cancelled, depending on the venue's and the broker's rules rather than on anything the holder chose. An unadjusted order at an unadjusted price after a split is an instruction to trade at a price that no longer means what it meant.

Cancellation is a request, not an event. A cancel instruction must reach the venue before the order is matched, and in fast markets it may not. An order believed cancelled can still fill, which is a property of the sequence rather than a malfunction.

Outside regular hours

Extended-hours trading is a different environment wearing the same interface. Fewer participants, shallower books and wider spreads arrive together, and news is frequently released precisely then.

Worked example — the same instruction, twelve and a half times the cost. A 100-share round trip costs $4.00 in the active session and $50.00 in the thin one — a ratio of 12.5×, with nothing changed except the conditions the order met. The reason the two arrive together is that the spread is the price of immediacy, and immediacy is dearer when fewer participants are available to supply it. The compounding factor is that the reason someone wants to trade outside hours is usually that something has just been announced — so the moment of greatest urgency coincides with the moment of thinnest liquidity, and the cost of acting is highest exactly when the impulse to act is strongest. MarketClue characterises no session as thin, publishes no threshold for an acceptable spread and does not suggest when anyone should or should not transact. Figures are illustrative and describe no actual security.