Time-in-Force Orders: Day, GTC, IOC, FOK and AON Explained

Time-in-Force Orders: Day, GTC, IOC, FOK and AON Explained

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A limit price answers what price is acceptable. A time-in-force instruction answers how long the order may remain active and whether a partial fill is acceptable. Traders who confuse those two decisions can leave stale orders working, receive only part of the position they expected, or cancel an order that was behaving exactly as instructed.

This tutorial explains Day, Good-Til-Cancelled (GTC), Immediate-Or-Cancel (IOC), Fill-Or-Kill (FOK) and All-Or-None (AON) instructions. The exact names, availability, session rules and maximum duration vary by broker, venue and asset class, so the order ticket and broker policy always take precedence.

Learning objective

By the end, you should be able to:

1. Separate price instructions from time-in-force instructions.
2. Choose between Day, GTC, IOC, FOK and AON based on the execution objective.
3. Predict whether an order may rest, expire or receive a partial fill.
4. Check the practical risks before submitting or leaving an order open.

Start with two separate questions

Every order needs an execution method. Ask:

• Price question: Am I willing to trade at the best available price, or only at a stated limit price or better?
• Duration and quantity question: Must the order trade now, can it wait, and may it fill partially?

Market and limit are price-related order types. Day, GTC, IOC and FOK are commonly called time-in-force instructions. AON is mainly a quantity condition, although it affects how long an order can wait. A platform may combine these instructions differently or refuse some combinations.

Day order: active for the current trading day

A Day order normally expires if it has not filled by the end of the relevant trading session. It is useful when the reason for trading applies only today and you do not want the instruction to remain active overnight.

Suppose a share trades near £25 and you enter a Day limit buy at £24.60. If the market never reaches an executable price during that session, the order expires. It does not automatically return the following morning.

The phrase “end of day” can be less simple than it sounds. Some brokers distinguish regular-hours, extended-hours and auction sessions. Confirm which session the order covers and whether the broker automatically cancels it before or after the closing auction.

GTC: stays active until filled, cancelled or expired by policy

A Good-Til-Cancelled order remains working until it executes, you cancel it, or the broker's maximum duration or another rule ends it. Despite the name, GTC does not necessarily mean forever. Brokers commonly impose their own expiry periods.

GTC can suit a patient entry or exit at a carefully chosen price, but it creates stale-order risk. New earnings, a dividend, a stock split, a regulatory event or a changed trading thesis can make yesterday's limit inappropriate. Some brokers adjust eligible open orders for corporate actions; policies differ.

Treat every GTC order as an open commitment. Review it after major news and reconcile it with the position size and cash still available.

IOC: take what is available now and cancel the rest

An Immediate-Or-Cancel order attempts to execute immediately. Any quantity that cannot be filled at once is cancelled. Partial fills are allowed.

Assume the visible offers are:

Offer price	Shares available
£10.00	300
£10.01	500

You submit an IOC limit buy for 600 shares at £10.00. If the displayed liquidity is still available when the order arrives, up to 300 shares may fill at £10.00 and the remaining 300 are cancelled. The order does not wait for another seller at £10.00.

IOC is useful when the trader wants immediate liquidity but does not want an unfilled balance resting in the book. The fill can still differ from the screen because quotes change, other orders reach the venue first, and liquidity may be distributed across venues.

FOK: fill the complete quantity immediately or cancel everything

A Fill-Or-Kill order must execute immediately in full; otherwise the whole order is cancelled. Partial fills are not accepted under the standard definition used by the SEC's investor education material and FINRA.

Using the same order book, an FOK limit buy for 600 shares at £10.00 should cancel because only 300 shares are available at the permitted price. An FOK limit buy for 250 shares may execute in full if the liquidity remains when the order reaches the market.

FOK can help when a partial position would be operationally useless or would leave an unwanted hedge mismatch. It also lowers the probability of any execution, especially in a thin market or for a large order. Venue definitions and supported combinations can differ, so confirm the broker's implementation.

AON: complete quantity required, but not necessarily immediately

An All-Or-None instruction requires the full quantity to be executed or none of it. Unlike FOK, immediate execution is not required. An AON order may remain active while waiting for the full quantity, subject to its other duration instruction and the broker's rules.

For example, an AON limit buy for 600 shares at £10.00 could remain pending when only 300 shares are available. It may execute later if enough eligible liquidity appears. It may also receive no fill even though smaller trades occur at the limit price.

Availability is not universal, and AON orders may receive different handling or priority. Do not assume that seeing the market trade at your limit means the full AON quantity was available to your order.

Worked example: one idea, five different outcomes

A trader wants to buy 1,000 shares of a hypothetical company. The maximum acceptable price is £20.00. At the moment of submission, 400 shares are offered at £20.00 and another 900 at £20.03.

Day limit buy: 1,000 at £20.00

Up to 400 shares could fill immediately. The remaining 600 can rest until later in the session and may fill if sellers appear at £20.00. Any unfilled balance normally expires at the end of the applicable session.

GTC limit buy: 1,000 at £20.00

The immediate result may also be a 400-share partial fill. The remaining 600 can continue working across sessions until filled, cancelled or expired under broker policy. The trader must keep reviewing whether £20.00 is still appropriate.

IOC limit buy: 1,000 at £20.00

Up to 400 shares may execute immediately, and the other 600 are cancelled. The trader finishes with a smaller position and must decide separately whether to send another order.

FOK limit buy: 1,000 at £20.00

The entire order cancels because 1,000 shares are not immediately available at £20.00 or better. The trader receives no position.

AON limit buy: 1,000 at £20.00

The order receives no 400-share partial fill. Depending on its duration and broker handling, it may wait for the full 1,000 shares to become executable or eventually expire or be cancelled.

This comparison shows why the same limit price and quantity do not guarantee the same result. The time and quantity instruction changes the execution behaviour.

A simple decision framework

Use the execution objective to narrow the choice:

• The idea is valid only today: consider a Day limit order.
• The price matters and you are prepared to wait: consider GTC, with a scheduled review process.
• You want available liquidity now but accept a smaller fill: consider IOC.
• You need the complete position immediately or nothing: consider FOK.
• You need the complete quantity but can wait: consider AON if the broker supports it.

This is a functional comparison, not a recommendation. Large orders may require a staged execution plan rather than a single special instruction.

Common mistakes

Assuming GTC means permanent

Broker expiry rules can end a GTC order. Corporate actions or venue rules may also change its treatment.

Expecting an IOC order to fill completely

IOC allows a partial fill. Only the unfilled balance is cancelled.

Treating FOK and AON as identical

Both reject partial execution, but FOK also demands immediate execution. AON can wait.

Forgetting that visible size can disappear

The order book is a moving snapshot. Displayed liquidity may trade or be cancelled before your order arrives.

Leaving an old GTC order after the thesis changes

A technically valid order can become strategically wrong. Open-order review is part of risk management.

Ignoring partial-position risk

An IOC or ordinary limit order can create a smaller position than planned. That matters when the trade is paired with a hedge, another leg or a minimum economic size.

Practical checklist before submitting

• Is this a market, limit, stop or stop-limit order?
• What is the exact time-in-force instruction?
• Are partial fills acceptable?
• Which trading session does the instruction cover?
• When will the broker expire a GTC order?
• Could a partial fill leave an unhedged or uneconomic position?
• Is sufficient cash or margin available if an old GTC order executes?
• Will fees make several small fills expensive?
• Have corporate actions or new information changed the intended price?
• Is there a routine for reviewing and cancelling stale orders?

Sources and further reading

The SEC's Investor.gov guide explains market, limit and stop orders, while its Trading Basics publication defines Day, GTC, IOC, FOK and AON instructions. FINRA's investor guide compares the same order types and timing conditions. Nasdaq's official market-model documentation also shows that time-in-force availability depends on the order type and market state.

For the related mechanics, read our guides to market, limit and stop orders, the order book and market depth, and bid-ask spread and slippage.

This tutorial was prepared with AI-assisted research and editorial review. It is educational information, not personalised investment advice. Order availability and handling differ by broker, venue and asset class. Execution, price and liquidity are never guaranteed, and trading can result in loss.