Stop Order

What Is a Stop Order?

A stop order is an instruction to buy or sell a security once its market price reaches a set level, called the stop price. Until that level is reached, the order stays inactive and is not sent to the market. Once the stop price is hit, the order becomes live. In its most common form it becomes a market order, which fills at the best available price. In a variant called a stop-limit order, it becomes a limit order instead.

How a Stop Order Works

A sell stop is placed below the current price. If the price falls to the stop level, the order triggers and the shares are sold. A buy stop is placed above the current price and triggers if the price rises to that level. Investors often use sell stops to limit potential losses on a holding. Buy stops are commonly used to limit losses on a short selling position or to enter a position after an upward move.

The key point is what happens after the trigger. A standard stop order becomes a market order, so the fill price may differ from the stop price. In a fast-moving or thinly traded market, the fill can be meaningfully worse than the stop price. This gap is known as slippage. A stop-limit order reduces that price uncertainty, but it may not fill at all if the market moves past its limit price.

Example

Consider a hypothetical investor who buys shares at 50 dollars and places a sell stop at 45 dollars. If the price falls to 45, the stop triggers and a market order to sell is sent. If the market is moving quickly, the next available trade might occur at 44. The shares would then sell at 44, and the difference from the stop price is the slippage. A stop-limit order with a limit of 44 would have avoided that lower fill, but it might not have executed at all if the price kept falling below 44.

Advantages and Limitations

Stop orders are simple to set and do not require constant monitoring, which can help an investor follow a predefined exit plan. However, they do not guarantee execution at the stop price, especially around market openings or sudden price gaps. Prices can also briefly touch a stop level during normal volatility and trigger a sale before the price recovers. Understanding these tradeoffs is an important part of using stop orders.