Fill-or-Kill vs immediate-or-cancel: which cancels faster?

12 October 2026

Fill-or-Kill (FOK) and Immediate-or-Cancel (IOC) both cancel unfilled portions of an order immediately, but FOK cancels the entire order if it cannot be filled completely, while IOC cancels only the unfilled part and allows a partial fill. This difference means IOC is the faster cancellation in practice, because FOK requires a brief evaluation period to determine whether the full quantity can be filled before it cancels everything.

How each order type works

Both FOK and IOC are time-in-force instructions that tell an exchange how long to keep an order active. Neither allows the order to rest on the order book. The key difference is what happens when the order cannot be filled entirely at once.

Fill-or-Kill (FOK)

• The order must be filled in its entirety immediately or not at all.
• If matching liquidity exists for the full quantity, the order executes completely.
• If any part of the order cannot be filled, the entire order is cancelled - nothing is filled.
• FOK is commonly used when you need to execute a specific block of a cryptocurrency without leaving a trace or partially filling a position.

Immediate-or-Cancel (IOC)

• The order fills any available quantity immediately, then cancels the remainder.
• A partial fill is allowed. If only 2 BTC out of a 5 BTC order are available, you get 2 BTC and the other 3 BTC are cancelled.
• IOC is useful when you want to get some liquidity quickly but do not require the full order to fill right now.

Which Cancels Faster?

The cancellation itself is nearly instantaneous for both types - typically within milliseconds. However, the answer depends on what you mean by "faster cancellation."

Cancellation of the order itself

IOC cancels the unfilled portion immediately after the partial fill. FOK must first determine whether the full order can be filled, then cancel everything if it cannot. This determination takes a tiny amount of time (often microseconds to a few milliseconds) while the exchange checks the order book depth. So IOC technically cancels faster because it does not wait for a full-order viability check.

Cancellation of your intended trade

If your goal is to get out of the market quickly after failing to fill, FOK cancels the entire order, including any fill that might have happened. But if a partial fill occurs under IOC, you are left with a smaller position that you may need to handle separately. So FOK can be seen as "faster" in terms of wiping your order from the book entirely.

When to use each

Use Fill-or-Kill when

• You need to execute a precise quantity - for example, buying exactly 10 ETH as part of a larger strategy where a partial fill would break your plan.
• You want to avoid leaving any order history visible. FOK either fills completely or disappears, so no partial fill remains on your record.
• You are trading illiquid pairs where a partial fill would distort your average entry price.

Use Immediate-or-Cancel when

• You want to grab available liquidity quickly without waiting for a full order book match.
• A partial fill is acceptable - you can later fill the remainder with another order.
• You are testing market depth or trying to get a small position started without commitment.

Practical considerations on munchcoin.xyz

• Exchange support: Not every exchange supports both FOK and IOC. Some platforms only offer one or the other. Check the exchange's order type documentation before assuming availability.
• Fees: Both order types may incur taker fees because they consume liquidity from the order book. Maker fees typically apply only to resting limit orders.
• Slippage: Because both orders execute immediately against available liquidity, they are subject to the same slippage risks as market orders. If the order book is thin, you may get a worse price than expected.
• Large orders: For very large orders, FOK may fail frequently because the full quantity is rarely available. IOC gives you at least some execution, which can be helpful in volatile markets.

Common Misunderstandings

• FOK does not guarantee a better price. It only guarantees that you get the full quantity or none. The price you receive depends on the order book at that moment.
• IOC does not cancel faster because it is "immediate". The time difference is negligible for most traders. The practical difference is the partial fill behavior.
• Neither is a "hidden" order. Both are visible to the exchange and may affect the order book temporarily during the matching process.

Summary

If you need the entire order to cancel - including any attempted fill - FOK cancels faster in the sense that your order disappears cleanly. If you want the unfilled portion to cancel without waiting for a full viability check, IOC cancels faster. For most retail traders, the difference in cancellation speed is not noticeable; choose based on whether you need a full fill (FOK) or accept a partial one (IOC).

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