IOC Orders in Trading: What Immediate or Cancel Means for Execution
BY TIOmarkets
|March 24, 2026An Immediate or Cancel order, commonly abbreviated as IOC, is an instruction that tells a broker or exchange to fill as much of an order as possible at the current available price and immediately cancel any portion that cannot be filled. Unlike a standard market order that executes in full, an IOC order accepts partial execution and discards the remainder rather than waiting for the full quantity to become available.
Understanding how IOC orders work, when they are useful, and how they compare to other fill policies helps traders make more deliberate decisions about order execution, particularly in markets where liquidity and execution speed matter.
How an IOC Order Works
When you submit an IOC order, the platform or broker attempts to execute it immediately at the best available price. If the full quantity is available at that price, the order fills in full. If only part of the quantity is available, the order fills partially and the unfilled remainder is cancelled immediately without being queued or resting in the order book.
The defining characteristic is the combination of immediacy and the acceptance of partial fills. The order does not wait. Whatever can be executed right now is executed. Whatever cannot be executed right now is cancelled.
This distinguishes IOC from two other common fill policies. A Fill or Kill order requires the entire quantity to be filled immediately or the whole order is cancelled with no partial execution. A standard resting order, sometimes described as a Return or Good Till Cancelled policy, leaves unfilled portions in the market as a pending order waiting for the price to return and complete the fill.
IOC sits between these two: it accepts whatever is immediately available, like a Return policy, but cancels the remainder rather than leaving it open, unlike a Return policy.
IOC vs Fill or Kill vs Return
The three fill policies represent different trade-offs between certainty of execution, certainty of quantity, and willingness to leave orders open.
A Fill or Kill order prioritises quantity certainty. Either the entire order is filled at once or nothing executes. This is useful when partial execution would leave the trader with an unintended position size that does not serve the purpose of the trade. The risk is that if full liquidity is not available immediately, the order is cancelled entirely and no position is opened.
An IOC order prioritises execution speed while accepting the possibility of a partial fill. The trader gets whatever is available at the current price right now, and the remainder is cancelled. This suits situations where immediate execution of at least part of the order is preferable to no execution at all, but where leaving a partial remainder open as a resting order is not desired.
A Return or Good Till Cancelled policy prioritises completeness over immediacy. Any unfilled portion remains as a pending order in the market, waiting for the price or liquidity to return and fill the rest. This is the most common approach for traders who want full execution and are willing to wait, but it introduces the possibility that the remainder fills later at a different price or under different market conditions.
The right choice depends on why the order is being placed, how important the specific quantity is, and whether partial execution at the current moment serves the trading objective better than waiting for full execution later.
When IOC Orders Are Used
IOC orders are most relevant in contexts where speed of execution matters and partial fills are acceptable.
In markets with variable liquidity, the full quantity of a large order may not be available at a single price level at a given moment. An IOC order captures whatever liquidity exists at that level immediately and cancels the rest, rather than breaking the order across multiple price levels as a standard market order might do, or waiting for liquidity to return as a resting order would.
For strategies that require entry at a specific price level but not necessarily the full intended size, IOC allows partial execution without the risk of the remainder filling later at a worse price. If the opportunity at the target price passes, the unexecuted portion is simply cancelled rather than remaining as a pending order that might fill under different conditions.
Algorithmic and automated trading systems sometimes use IOC orders as part of larger execution strategies, submitting multiple partial orders to different liquidity sources simultaneously and cancelling whatever does not fill at the target conditions.
In fast-moving markets, the combination of immediate execution and automatic cancellation of the remainder removes the risk of a resting order being filled later at an unfavourable price that has moved away from the original intent.
IOC Orders and Partial Fills
The practical consequence of an IOC order is that you may end up with a smaller position than intended. If you submitted an IOC order for 1.0 lots and only 0.6 lots of liquidity was available at the target price, your resulting position is 0.6 lots and the remaining 0.4 lots is cancelled.
This requires the trader to be prepared for the possibility of a partial fill and to have a clear view of how the resulting position size affects the trade's risk profile. A position that is smaller than intended will have a different margin requirement, different pip value, and different dollar exposure than the planned trade.
For traders using fixed position sizing rules tied to account equity, a partial fill means the risk on the trade is proportionally smaller than planned, which is generally preferable to a position that is larger than intended. However, it also means the trade may not fully express the intended directional view.
IOC Orders on MetaTrader Platforms
MetaTrader 4 and MetaTrader 5 handle order fill policies differently, and this distinction is relevant for traders who use IOC orders.
MetaTrader 4 supports one fill policy: Fill or Kill. Orders submitted on MT4 must be filled in full immediately or they are cancelled entirely. Partial fills and resting remainder orders are not available as fill policy options on MT4. The IOC fill policy is not available on MT4.
MetaTrader 5 supports three fill policies: Fill or Kill, Immediate or Cancel, and Return. The IOC option is available on MT5, allowing traders to specify that partial fills are acceptable and the remainder should be cancelled rather than resting in the market. The availability of specific fill policies for a given instrument on MT5 depends on the instrument and the broker's configuration.
This is one of the practical execution differences between the two platforms. Traders who require IOC order functionality need MT5 rather than MT4.
IOC in the Context of Forex and CFD Trading
In retail forex and CFD trading, the relevance of IOC orders is somewhat different from institutional equity markets, where large order sizes and fragmented liquidity across multiple venues make fill policy decisions a significant part of execution management.
In retail CFD trading, most market orders on major instruments fill at a single price in milliseconds, meaning the distinction between IOC, FOK, and Return is less frequently meaningful in practice. The full order quantity is typically available at the quoted price for standard retail lot sizes.
The fill policy distinction becomes more relevant for larger position sizes, for instruments with lower liquidity, for trading during conditions where the spread is wide and liquidity is thinner, or for traders using algorithmic strategies where execution precision is a formal part of the strategy's logic.
Understanding fill policies is also useful for traders who are building or evaluating automated strategies in MT5, where the fill policy parameter is part of the order submission and affects how the strategy behaves in different liquidity conditions.
Slippage and Fill Policy
Fill policy and slippage are related but distinct concepts. Fill policy governs whether a partial fill is acceptable and what happens to the remainder. Slippage governs the price at which execution occurs relative to the requested price.
An IOC order specifies how quantity is handled. It does not prevent slippage, meaning the portion that does fill may still execute at a slightly different price from the one requested if market conditions shifted between order submission and execution. Orders are executed at the best available market price, which may result in positive or negative slippage during volatile market conditions.
Both fill policy and slippage tolerance are part of the broader set of execution parameters that traders can define when constructing their order management approach.
Trading at TIOmarkets
TIOmarkets offers trading on forex, indices, stocks, commodities, and crypto CFDs through MT4 and MT5 on desktop, web, and mobile. MT5 supports three order fill policies: Fill or Kill, Immediate or Cancel, and Return. MT4 supports one fill policy: Fill or Kill. A Standard account is created automatically on registration. Raw and VIP Black accounts are opened separately via the client area. All accounts support hedging.
A swap-free Islamic account is available: contact TIOmarkets for eligibility and instrument details. Copy trading is also available, allowing followers to copy strategy providers in real time across MT4 and MT5.
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