A market on close order tells your broker to buy or sell a stock at whatever single price comes out of the exchange’s end-of-day closing auction, which runs at 4:00 PM ET. You trade price certainty for execution certainty: as long as there is liquidity in the auction, you get filled, but you won’t know the exact price until after the bell. Every participant in that auction receives the same price, which is why index funds, ETFs, and anyone who needs to transact at the official closing print rely on these orders.1New York Stock Exchange. NYSE Opening and Closing Auctions Fact Sheet
What You Get and What You Give Up
An MOC order prioritizes guaranteed execution over price control. Unlike a limit order, there’s no floor or ceiling you set. The exchange collects all pending buy and sell interest at the close, calculates the single price that matches the maximum number of shares, and fills every MOC order at that price regardless of when it was entered during the submission window.
The appeal is straightforward. Mutual funds value their holdings at the official close. ETFs calculate net asset value from the same prices after the bell. Any trade executed earlier in the day would almost certainly fill at a different price than the closing valuation, which creates tracking error for anyone benchmarking against that close. An MOC order closes that gap. For a retail investor, the use case is similar in spirit: if you want to transact at the price that will appear in historical charts and end-of-day quotes, this is the order type that gets you there.
How to Place a Market on Close Order
Most brokerage platforms list MOC in the order-type dropdown, sometimes written out as “Market on Close.” Selecting it grays out the limit-price field because the auction sets your fill. You enter the ticker, choose buy or sell, and specify the share count.
Confirm your account can cover the trade before submitting. A buy order requires settled cash or available margin, and because you won’t know the fill price until after 4:00 PM, your broker may hold a cushion above the current market price when calculating buying power. If the auction clears higher than your available funds, the broker can liquidate the position or issue a margin call, and some brokers charge a fee for forced liquidations. For a sell, you need to actually hold the shares.
You don’t need to trade in round lots. Odd-lot orders of fewer than 100 shares are eligible for both the NYSE and Nasdaq closing auctions.2Nasdaq Trader. The Nasdaq Opening and Closing Crosses Frequently Asked Questions
Submission Deadlines on NYSE and Nasdaq
The two major U.S. exchanges run slightly different clocks, and the difference matters if you’re cutting it close.
On the NYSE, MOC orders must be entered, modified, or canceled by 3:50 PM ET. After that, the order is locked.3New York Stock Exchange. NYSE Auctions Closing Process Fact Sheet On Nasdaq, modification or cancellation also stops at 3:50 PM, but new MOC orders are still accepted until 3:55 PM.4Nasdaq Trader. Nasdaq Closing Cross Frequently Asked Questions Cboe BZX, which runs its own closing auction, uses a 3:55 PM cutoff and prohibits modifications after that point.5Federal Register. Self-Regulatory Organizations; Cboe BZX Exchange, Inc.; Notice of Filing and Immediate Effectiveness of a Proposed Rule Change To Amend Rule 11.23
If a security is listed on one exchange but your broker routes the order elsewhere, the receiving venue’s rules govern. Most retail brokers handle routing automatically; if you’re unsure, ask before relying on a specific cutoff. Attempts to enter an order after the deadline are typically blocked at the platform level rather than sent to the exchange.
Cancellation Once the Cutoff Passes
After the submission deadline, you’re largely committed, and the rules are deliberately strict. Letting traders yank large orders seconds before 4:00 PM would allow fake imbalances to distort the official close, which anchors trillions of dollars in fund valuations, derivatives, and margin calculations.
On the NYSE, the timeline runs as follows:3New York Stock Exchange. NYSE Auctions Closing Process Fact Sheet
- Before 3:50 PM, you can freely enter, modify, or cancel.
- From 3:50 PM to 3:58 PM, cancellations are allowed only for documented errors.
- After 3:58 PM, electronic cancellations are rejected; any cancel request must go through the NYSE Trade Desk.
On Nasdaq, MOC orders are locked against both cancellation and modification at 3:50 PM, even while new entries remain open until 3:55 PM. The practical rule: review your order carefully before submitting, because once the clock crosses 3:50 PM, you’re almost certainly stuck with it.
How the Closing Price Gets Set
After the entry cutoff, the exchange begins broadcasting imbalance data: whether buy or sell interest is heavier, how many shares are paired off, and an indicative price. This information is designed to attract additional liquidity. If a large buy imbalance appears, other traders can step in with offsetting sell interest to help stabilize the close.6New York Stock Exchange. Order Imbalances Feed Client Specification
At 4:00 PM, the exchange runs the final match, calculates the single price that maximizes shares traded, and that price becomes the official close. Your broker sends a confirmation shortly after showing the fill price, share count, and any fees.
Auction Collars and Partial Fills
Exchanges cap how far the auction price can move. Auction collars set price boundaries as a percentage from a reference price (typically the last round-lot trade before the auction). On NYSE Arca, the collar bands are:7Securities and Exchange Commission. Rules of NYSE Arca Equities, Inc. – Exhibit 5
- Stocks priced $25 or below: 5 percent.
- Stocks priced $25.01 to $50: 2 percent.
- Stocks above $50: 1 percent.
If the clearing price would land outside the collar, auction-only orders that can’t fill within the band get canceled rather than executed at an extreme price. That protects you from a wildly distorted close, but it also means a sliver of your MOC order could go unfilled in rare, highly volatile moments. For liquid stocks on ordinary days, the collar is rarely tested.
Slippage and Thin-Stock Risk
The core risk is that the auction price differs meaningfully from where the stock traded minutes earlier. On liquid large-cap names during normal conditions, the gap between the 3:59 PM print and the auction price is usually small. On earnings days, index rebalancing events, or in volatile markets, the gap can widen enough to surprise you.
The problem is sharper for thinly traded stocks, where even modest imbalances can push the auction price several percentage points. If the auction doesn’t have enough opposing interest to absorb your size without moving the price, you’ll feel it in the fill. Collars help at the extremes, but they work by canceling unfilled shares, not by guaranteeing a reasonable price.
When a Limit on Close Order Makes More Sense
If the open-ended price exposure of an MOC order bothers you, a limit on close (LOC) order is the alternative. An LOC executes only in the closing auction, like an MOC, but adds a limit price. If the auction clears outside your limit, you simply don’t get filled.
On the NYSE, LOC orders follow the same 3:50 PM entry deadline as MOC orders and also cannot be modified or canceled afterward.1New York Stock Exchange. NYSE Opening and Closing Auctions Fact Sheet One exception: new LOC orders on the opposite side of a significant imbalance can be entered between 3:50 PM and 4:00 PM, which exists specifically to pull in liquidity when the auction is lopsided.
The tradeoff is clean. MOC guarantees execution but not price. LOC guarantees price but not execution. If your reason for trading at the close is specifically to match the official closing price for benchmarking, MOC is the right tool. If you want closing-auction participation but refuse to accept a bad fill, LOC is the right tool.
Settlement and Year-End Tax Timing
U.S. equity trades settle on a T+1 basis, meaning one business day after the trade date. An MOC order executed Monday at 4:00 PM settles Tuesday. This shortened cycle took effect on May 28, 2024, replacing the previous T+2 standard.8Securities and Exchange Commission. SEC Chair Gensler Statement on Upcoming Implementation of T+1
For most tax calculations, the trade date controls, not the settlement date. That matters at year-end: a losing position sold through an MOC order on December 31 counts as a current-year transaction even if settlement falls in January.
The wash sale rule also runs off the trade date. Under federal tax law, a loss deduction is disallowed if you buy substantially identical stock within 30 days before or after the sale.9Office of the Law Revision Counsel. 26 USC 1091 – Loss From Wash Sales of Stock or Securities So an MOC sell on December 15 means you’d need to stay out of that security until January 15 to preserve the loss. If you’re using closing-auction orders for tax-loss harvesting, map those dates before you submit.
Manipulation Rules You Should Know About
Deliberately placing orders to distort the closing print is known as “marking the close,” and regulators treat it as a manipulative scheme. FINRA’s 2026 Annual Regulatory Oversight Report identifies it specifically among the trading practices brokerage firms must surveil, with findings against firms that use weak alert thresholds or fail to document reviews.10FINRA. 2026 FINRA Annual Regulatory Oversight Report – Manipulative Trading
For an ordinary retail trader, the realistic compliance issue isn’t manipulation; it’s trying to cancel after the cutoff. Brokers generally block the attempt before it reaches the exchange, but the safe habit is to treat every MOC order as final the moment the clock crosses the exchange’s deadline. If you’re short selling at the close, additional obligations under Regulation SHO apply, including order marking and locate requirements that your broker enforces before accepting the order.11eCFR. Regulation SHO – Regulation of Short Sales