A Market on Close (MOC) order is a market order that queues for execution at the official closing auction rather than filling immediately in the continuous session. It guarantees the trader participates in the closing print — the price that drives ETF and mutual fund NAV calculations — but provides no protection against where that print lands.
Key Takeaways
- NYSE MOC orders must be submitted by 3:45 PM ET; Nasdaq’s cutoff is 3:55 PM ET — miss the deadline and your order does not execute at the close.
- The closing auction price can differ from the last displayed quote by $0.10–$1.00+ because institutional MOC flow, not continuous trading, sets it.
- On major index rebalance days (Russell 2000 in late June, S&P 500 additions), individual stocks can move 1–5% in the final seconds due to concentrated MOC order flow.
How a MOC Order Works
When a trader submits a MOC order, the broker forwards it to the exchange’s closing auction queue. The order sits there, unexecuted, until the exchange runs its closing auction algorithm at 4:00 PM ET. That algorithm matches all queued MOC orders, Limit on Close (LOC) orders, and resting day-session limit orders to find a single clearing price — the official closing price.
NYSE’s closing auction typically represents 5–15% of a stock’s total daily volume, making it the single largest discrete liquidity event of the trading day. Passive index funds use MOC orders as their default execution method because they must track benchmark closing prices exactly. That institutional flow is what creates both the reliability and the risk of the MOC order type.
Submission deadlines:
- NYSE: 3:45 PM ET to submit; same cutoff to cancel (except for legitimate errors)
- Nasdaq: 3:55 PM ET to submit or cancel
After the cutoff, a MOC order is locked in. A trader cannot withdraw it because the price moved against them — the exchange only permits cancellations to fix documented entry errors.
Practical Example
A swing trader holds 200 shares of AAPL purchased at $178.50 and wants to exit at Friday’s close to avoid weekend gap risk. At 3:30 PM ET — well before NYSE’s 3:45 PM cutoff — they submit a MOC sell order.
At 3:59:59 PM, AAPL’s last displayed bid-ask spread shows a quote of $182.10. The closing auction, however, clears at $181.95 — 15 cents below the final quote — because a large institutional seller simultaneously placed a substantial MOC sell order, shifting the auction’s clearing price.
The trader receives $181.95 × 200 = $36,390. They captured the gain, but received $30 less than a well-timed limit order at the displayed price would have yielded.
The gap widens significantly in less liquid names. In a $15 mid-cap stock averaging 300,000 shares per day, the same mechanics could produce a $0.40–$0.80 difference between the last quote and the auction price — costing $80–$160 on a 200-share order.
A Market on Close order tells your broker to execute a trade at the stock’s official closing price rather than immediately. It guarantees you’ll trade at the close, but the exact price depends on what other buyers and sellers are doing in the final auction.
Common Mistakes
- Missing the submission deadline. Submitting a MOC order at 3:50 PM on NYSE means it does not fill. The order is typically rejected or converted to a next-day order, depending on the broker.
- Trading MOC on index rebalance days. The Russell 2000 annual rebalance (typically the last Friday of June) is the largest MOC event of the year. Rebalance-eligible small-cap stocks have seen 20–50× normal closing-auction volume, with documented abnormal returns of 20–40% in the days before the event that partially reverse afterward. Using a MOC order on these stocks that day means competing directly with multi-billion-dollar passive fund flows.
- Assuming MOC equals last-print price. Many traders submit a MOC order expecting to receive the price shown on their screen at 3:59 PM. The auction price is set by supply and demand across all queued orders, not the continuous market’s last trade.
- Ignoring LOC as an alternative. When price certainty matters, a Limit on Close order participates in the closing auction only if the auction price reaches your limit. The trade-off is the possibility of no fill — but that is often preferable to an unexpectedly bad auction price.
How JournalPlus Tracks MOC Orders
JournalPlus logs the execution price of every trade, including closing-auction fills, and compares it against the session’s closing reference price. Traders can tag orders by order type to filter MOC fills separately and measure how closing-auction slippage affects overall average loss and win metrics over time. This makes it straightforward to identify whether rebalance-day MOC usage is a recurring drag on performance.
