Market-on-close order
Also known as: MOC order
A market-on-close order instructs a to execute a trade at whatever price the produces, with no price limit attached. The order is submitted ahead of the close and feeds directly into the alongside every other closing order, guaranteeing execution at the official closing price regardless of what that price turns out to be.
This makes a market-on-close order the equivalent of a regular , prioritizing certainty of execution over any control on price. It is commonly used by and other who need to trade at the closing price specifically, since that is the price their performance gets measured against, rather than at some price during continuous trading that would not match the benchmark. An investor who wants that same certainty of hitting the close, but with the additional protection of a price limit, would use a instead.
Exchanges require market-on-close orders to be submitted before a set cutoff time ahead of the close, and cancellations after that point are typically restricted as well, so the order has to be placed with the closing plan already decided rather than adjusted at the last minute. Because a large volume of market-on-close orders funnels into the same auction, an imbalance heavily skewed toward buy or sell orders can itself move the closing price, which is why exchanges publish order imbalance information in the minutes leading up to the close.