Market vs. Limit Orders: Price Control and the Risk of Not Filling
Market orders prioritize execution, while limit orders set a price boundary. Partial-fill examples explain each order type's risks and what to check after submitting an order.
A market order attempts to execute against available orders without specifying a price. A limit order sets a maximum purchase price or minimum sale price. A market order can execute at a different price than expected, while a limit order may not fill your entire intended quantity.
Decide which risk to constrain
When prices move quickly or the order book is thin, a market order's average execution price can differ substantially from the last price shown just before you click. A market order also cannot overcome a trading halt or the absence of orders on the other side. A buy limit restricts execution to the limit price or lower, while a sell limit restricts execution to the limit price or higher. The specified number is an acceptable price boundary, rather than a requirement to trade only at that exact price.
A limit order can execute immediately
A buy limit above the best ask can immediately execute against more favorable sell orders within that boundary. It is therefore incorrect to assume that limit orders always sit in the book for a long time. Conversely, an order at the last price may remain unfilled because of orders ahead of it and available quantities. Detailed order types, time in force, and treatment of the unfilled balance after a partial execution vary by venue and broker. An order's name alone cannot tell you how it will behave in an overseas app.
An order is not finished until you check its execution
Accepted, partially filled, fully filled, and cancellation completed are different statuses. If you submit a new order after a partial fill and forget the remaining original order, you can buy more than intended. Execution can also occur between clicking cancel and the exchange processing the cancellation, so check the trade record. Recording quantity and acceptable prices beforehand, then comparing average execution price and total costs afterward, helps assess which order type suited your trade size. Calculating your maximum acceptable outlay before submitting also makes quantity-entry mistakes easier to catch. Multiply the buy limit by the order quantity, add expected costs, and compare the result with your available buying power. With a market order, this upper-bound calculation is not fixed, so check how the broker determines required funds. Make a habit of reading the outcome for each existing order number before rushing to submit another order.
Worked example
Hypothetical example: Suppose 80 shares are offered at KRW 5,000 and 120 at KRW 5,010. A limit order to buy 200 shares at KRW 5,000 may fill only 80 shares if conditions remain unchanged. With a KRW 5,010 limit, the full quantity can fill at those two prices, averaging KRW 5,006. KRW 5,010 is the ceiling; it does not mean every share must be bought at that price.
What to check
- Have you set a maximum purchase price or minimum sale price?
- Is there an unfilled balance after a partial execution?
- Have you checked the order's time in force and trading session?
Sources and primary materials
This is educational material about research methods. For an actual company decision, verify the filings and primary sources for the relevant period.