What is a Limit-on-Close (LOC) Order? Definition, Formula, and Example
A Limit-on-Close (LOC) order is a conditional order that executes at the market close only if the closing price is equal to or better than the specified limit price.
What is a Limit-on-Close (LOC) Order?
A Limit-on-Close (LOC) order is a conditional order type that guarantees execution at the closing auction price, but only if that final closing price is equal to or better than a limit price specified by the trader. If the market's closing price falls outside the trader's limit parameters, the order is automatically canceled and expires worthless. LOC orders allow market participants to price-control their end-of-day execution without forcing a trade at an unfavorable closing price. Retail and institutional traders rely on LOC orders to participate in the closing auction while capping their slippage risk.
How it's calculated / identified
An LOC order does not require a mathematical formula, but it follows strict exchange-matching logic. Traders submit the order with two parameters: the order quantity and the limit price. The exchange holds the order in its closing auction order book. At the market close (4:00 PM EST for US equities), the exchange calculates the closing auction price based on the aggregated supply and demand of all market-on-close (MOC) and LOC orders.
For buy orders, execution occurs if the final closing price is less than or equal to the limit price. For sell orders, execution occurs if the final closing price is greater than or equal to the limit price. If the closing auction price breaches the limit threshold, the order is canceled.
Worked example
Assume a trader wants to buy 1,000 shares of AAPL at the end of the trading day. AAPL is currently trading at $190.00 at 3:50 PM. The trader submits an LOC order with a limit price of $190.50.
At 4:00 PM, the exchange calculates the closing auction price based on the net imbalance of all closing orders. If the closing price prints at $190.25, the limit condition is met ($190.25 is less than $190.50), and the order executes 1,000 shares at $190.25. If a massive buy imbalance pushes the closing auction price to $191.00, the limit condition fails ($191.00 is greater than $190.50), and the order is canceled without executing.
When traders use it
Traders use LOC orders when they need end-of-day liquidity but want strict price protection against closing auction volatility. This is common for institutional portfolio managers rebalancing index funds at the close, who require closing liquidity but cannot pay arbitrary prices. Retail day traders also use LOC orders to exit intraday positions at the close while ensuring they do not pay a premium if a late-day imbalance spike inflates the closing print. Unlike standard limit orders, LOC orders are restricted to the closing auction and do not execute intraday.
Limitations / common misconceptions
A common misconception is that LOC orders guarantee execution at the exact limit price. The order executes at the final closing auction price, which is simply bounded by the limit. If the closing price is $189.00 and the buy limit is $190.50, the fill occurs at $189.00. Another limitation is partial fills. If the closing auction volume is insufficient to absorb all orders at the clearing price, LOC orders are subject to pro-rata allocation alongside MOC orders. Traders cannot use LOC orders to capture intraday momentum; they remain dormant until the closing auction.