Immediate-or-Cancel Order
An order that executes whatever quantity is available at once and cancels the remainder rather than resting in the book.
How it is identified
Test: any unfilled quantity is cancelled immediately on submission instead of joining the order book
Unit
qualitative
In depth
An IOC order is used when a trader wants to take existing liquidity without advertising a further intention — the residual never appears in the book, so it signals nothing. It is the standard building block of algorithmic execution, where a large parent order is worked as a stream of small IOCs. Partial fills are the normal outcome, not an error, which surprises traders who expect all-or-nothing behaviour. Where a complete fill is essential, an all-or-none instruction is the correct choice instead.
Worked example
An IOC buy for 5,000 shares meets only 1,800 available at the limit price. It fills 1,800, cancels the remaining 3,200 instantly, and leaves no trace in the book for other participants to react to.
Illustrative figures, chosen so the arithmetic is easy to follow. Not a live price and not a valuation of any company.
Educational reference only
This entry explains what “Immediate-or-Cancel Order” means. It is not investment advice and not a recommendation to buy or sell any security. Any numbers above are illustrative, not live prices, and nothing here predicts price direction or rates a stock. Consider your own circumstances and consult a SEBI-registered investment adviser before acting.