When the stop price is reached, a stop order becomes a market order, and a stop-limit order becomes a limit order that will be executed at a specified price or better. That single difference sets everything else: the stop gives up the execution price, the stop-limit gives up the execution. The SEC's own specification shows the shape of it — a sell stop-limit order with a stop price of $3.00 can carry a limit price of $2.50, becoming an active limit order when prices reach $3.00 but executing only at $2.50 or better. The condition that decides which one costs you is a gap straight through both prices.

The stop price is a trigger, not a fill price

The SEC's stop-orders bulletin, updated 18 August 2026, is blunt about it. The stop price is not the execution price for a stop order; it is a trigger that causes the stop order to become a market order, and the execution price can deviate significantly from the stop price because of the prices of available liquidity when the market order executes.

Direction is fixed by the rule, not by preference. A sell stop order is entered at a stop price below the current market price, and a buy stop order at a stop price above it. FINRA describes the same instrument as an order to buy or sell a security once the price reaches a specified price known as the stop price.

One more mechanical exposure sits inside the trigger. A stop order can be triggered by a short-term, intraday price move that results in an execution price substantially worse than the stock's closing price for the day.

The stop-limit trades execution for a price floor

An investor can avoid the risk of a stop order executing at an unexpected price by placing a stop-limit order, which includes a limit price requiring execution at the limit price or better, but the limit price can prevent the order from being executed.

The two prices are independent. The stop price and the limit price for a stop-limit order do not have to be the same price. Set them far apart and the order is likelier to fill at a worse price; set them close and the order is likelier not to fill at all. FINRA puts it as a stop order designed to trigger the activation of a limit order rather than a market order.

Example: 400 shares, a $3.00 stop and a $2.50 limit

What follows is an example of the mechanism, not a strategy. The $3.00 stop and $2.50 limit are the SEC bulletin's own figures; the overnight price path below is fictional, because no public figure fixes where a particular stock opens.

An account holds 400 shares bought at $4.00. The stock closes a session at $3.40. Overnight the stock gaps, and the next session opens at $2.20, never trading at $3.00 or $2.50 in between.

Run the plain sell stop at $3.00. The open at $2.20 satisfies the trigger, the order becomes a market order, and it executes against whatever bids exist: say $2.20. Proceeds are 400 times $2.20, or $880. Against the $4.00 basis that is 400 times $1.80, or $720 below cost, and the fill sits $0.80 under the stop price that triggered it. The position is closed.

Run the sell stop-limit with the $3.00 stop and the $2.50 limit instead. The same open triggers it, and it becomes a limit order at $2.50. A sell limit order can only be executed at the limit price or higher, and the market is $2.20, so nothing executes. The 400 shares are still held, and the order rests until it fills, expires or is canceled. If the stock later trades back to $2.50 and the order fills there, proceeds are 400 times $2.50, or $1,000 — $120 more than the stop produced, and only because the price came back.

What fires the trigger varies by venue and firm

Before either order behaves, something has to decide that the stop price was reached. Different brokerage firms have different standards for determining whether a stop price has been reached: some use only last-sale prices to trigger a stop order, while others use quotation prices, and the same divergence applies to stop-limit orders.

That is a house-by-house answer, and it changes when your order wakes up in a fast market. It is also why a stop is not a floor under a position and why a triggered stop inherits the whole distance between a quote and a fill. The underlying pair is still a market order and a limit order, each arriving one step later than usual.

Source references

Primary sources used for this guide. Follow the links for the original scope, definitions and conditions.