What Is a Market-on-Close (MOC) Order? When It Executes

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A market-on-close (MOC) order is an instruction to buy or sell a security at the official closing price of the trading session. It is a market order with a timing condition: it carries no price limit, it waits until the close, and it executes in the exchange’s closing process at whatever price that process sets. An MOC order secures participation at the close. It does not secure a particular price.

How a market-on-close order executes

An MOC order is dormant from the moment you submit it until the close. It does not interact with the continuous order book during the day, so intraday prices have no effect on it. As the session ends, the exchange collects all orders flagged for the close, including MOC orders and limit-on-close orders, and runs an auction that matches as much buy and sell volume as possible at a single price. That auction price becomes the official closing price, and every MOC order that executes is filled at it.

Timing rules set MOC orders apart from an ordinary market order sent at 3:59 p.m. Exchanges require MOC orders to arrive before a published cutoff and restrict cancellations or changes after it. The exchange publishes imbalance information (how much more buy than sell interest is waiting, or the reverse) ahead of the auction, and late cancellations would make that information unreliable.

An MOC imbalance is the gap between closing buy and sell interest. When the imbalance is large, the auction price moves to attract offsetting orders. A heavy sell imbalance can push the closing price below the last trades of the session, which traders call an MOC selloff. A buy imbalance can lift the close in the same way.

Worked example

Hypothetical, for illustration only. A trader holds 100 shares of ABC, which reports earnings after the closing bell, and does not want to carry the position overnight. At 2:30 p.m. the stock trades at $50.00. The trader enters an MOC sell order and leaves the screen.

In the closing auction, sell interest outweighs buy interest, and the official close prints at $48.20. The order fills at that price:

Proceeds = shares × closing price = 100 × $48.20 = $4,820 (before commissions and fees)

That is $180 less than the 2:30 p.m. price would have produced, but the trader still exits before the earnings release, which was the goal. Had the close been $50.40, the trader would have received $5,040. The order controls when the trade happens. The auction decides at what price.

Why traders use MOC orders

• Avoiding overnight event risk. Earnings, economic releases or news expected after the close can gap a stock at the next open. An MOC order trades before that risk begins.
• Matching a benchmark. Index funds and many institutional portfolios are measured against closing prices, and mutual fund net asset values are calculated from them. Trading at the close aligns the execution price with the benchmark, which matters around index rebalancing dates.
• Being unavailable at the close. A trader who will be away, or who trades a foreign exchange in another time zone, can place the order hours in advance.
• Backing up a limit order. A trader may work a limit order during the day and complete the trade at the close if the limit is never reached. This guarantees the trade is done but reintroduces end-of-day price exposure.

Limitations and risks

The main drawback is price uncertainty. You learn the fill price only after the close, and a volatile final session or a large imbalance can produce a closing price well away from the intraday range you saw. Thinly traded securities can see poor execution, while large, liquid stocks tend to have deep closing auctions.

Commitment is the second limit. After the exchange cutoff, exchanges generally do not accept cancellations or changes except to correct a genuine error, even if news breaks in the final minutes. The order also does nothing to manage risk during the session. A position that falls sharply at 11 a.m. is not protected by an MOC order, which is the job of a stop-loss order.

MOC compared with related orders

• Market order: executes immediately at the best available price during continuous trading. An MOC order waits for the closing auction.
• Limit-on-close (LOC): participates in the closing auction only if the closing price is at or better than your limit. It controls price but may not fill.
• Market-on-open (MOO): the opening counterpart, filling in the opening auction at the official opening price.
• Day order: a time-in-force instruction that cancels any unfilled portion at the end of the session. It says when an order expires, not that it trades at the close.
• Last trade vs. closing price: the final trade printed before 4:00 p.m. is not necessarily the official close. MOC orders fill at the auction price, which becomes the official close.

FAQs

The Bottom Line

MOC orders suit traders who need to exit before after-hours news, match a closing-price benchmark, or cannot watch the close. They guarantee timing but leave the fill price to the auction, so large imbalances or thin trading can produce a close well away from earlier prices. Traders who need price control can use a limit-on-close order and accept that it may not fill.