Execution & trading costs

Stop-limit order

Stop-limit order is an instruction that, once a specified stop price is reached, becomes a limit order that can execute only at its limit price or better.

What it means

A stop-limit order has two price settings: a stop price that activates the order and a limit price that restricts its execution price. Once the stop is triggered, the instruction becomes a limit order. It may fill in full, fill partially, or remain unfilled.

A buy stop-limit order is commonly configured with a stop above the current price. After activation, it can execute at the buy limit or lower. A sell stop-limit order is commonly configured with a stop below the current price. After activation, it can execute at the sell limit or higher. The stop and limit can be the same price, but they do different jobs.

Trigger rules, available order settings, and how long an activated order remains open depend on the broker and trading venue. A stop trigger is not itself a trade.

How it is calculated

A stop-limit order is an instruction, not a calculated indicator. Its two inputs are prices, usually quoted in US$ per share for a US stock. The price condition after activation is:

buy execution price ≤ L; sell execution price ≥ L, provided the stop condition at S has triggered

  • S is the stop price, in US$ per share: the specified activation threshold under the broker’s trigger rules.
  • L is the limit price, in US$ per share: the worst permitted execution price for the order. For a buy, it is the maximum; for a sell, the minimum.

These inequalities describe eligible prices, not guaranteed fills. Execution also requires available shares at an eligible price and depends on the order’s time-in-force and applicable market rules.

Worked example

Assume a hypothetical stock trades around US$50 per share. An investor enters a sell stop-limit order for 100 shares, with a US$48 stop and a US$47 limit.

  1. If the broker’s trigger condition is met at US$48, the sell limit order becomes active. No sale has necessarily occurred.
  2. If enough eligible buying interest is available at US$47.50 per share, all 100 shares could fill there. Gross proceeds would be 100 × US$47.50 = US$4,750, before any fees.
  3. If only 40 shares are available at an eligible price before the order expires or is canceled, 40 could fill and 60 could remain unfilled, subject to the order’s settings.
  4. If the first available buying prices after activation are below US$47 and no eligible price becomes available while the order is active, nothing fills. The limit prevents a sale below US$47; it does not ensure a sale.

Why it matters before you trade

The distance between stop and limit prices defines a trade-off. A narrow gap restricts the permitted execution price more tightly but can increase the chance of no fill after a rapid move. A wider gap permits more execution prices but allows a less favorable fill within the limit. Neither setting eliminates gap risk.

Before placing an order, it helps to distinguish the intended trigger from the acceptable execution price and check the broker’s trigger rules, trading hours, time-in-force, and treatment of partial fills. Liquidity, bid-ask spread, volatility, and trading halts can affect whether an eligible price is available. A stop-limit order differs from a stop order that becomes a market order: the limit provides a price boundary but introduces non-execution risk.

How PreTrAIde uses it

PreTrAIde lets users specify execution conditions when building a stock basket for pre-trade analysis. Its analysis returns a GO, NO-GO, or MODIFY verdict, a risk assessment, a suggested execution strategy, and plain-language reasoning for the basket and each line. Its quantitative layer estimates spread, participation in daily volume, and market impact—factors relevant to assessing execution conditions.

The product facts do not state that PreTrAIde places stop-limit orders or determines their trigger mechanics. PreTrAIde does not receive, transmit, or execute orders; users place trades with their own broker. Its verdicts are decision support, not recommendations or assurances of execution.

Common mistakes

  • Treating the stop as a guaranteed fill price. It activates an order; the limit controls eligible execution prices afterward.
  • Assuming a limit guarantees a fill. The market may move beyond the limit without a matching trade.
  • Confusing the two prices. For a sell, a lower limit can allow a lower sale price; for a buy, a higher limit can allow a higher purchase price.
  • Ignoring order duration or partial fills. An unfilled balance may remain open or expire according to the selected settings.

Frequently asked questions

What happens when a stop-limit order is triggered?

It becomes a limit order. It can execute only at the limit price or better, and it may fill partially or not at all.

Why did my stop-limit order not fill?

After triggering, the market may not have offered enough shares at a price permitted by your limit. Order duration, trading hours, and broker or venue rules can also matter.

What is the difference between a stop-limit order and a stop order?

A stop-limit order becomes a limit order when triggered, retaining a price boundary but risking no fill. A stop order that becomes a market order seeks execution without that limit-price boundary.

Related terms

Stop order Stop order is an instruction that becomes a market order when a specified stop price is reached, so its execution price can differ from the stop price. Limit order Limit order is an instruction to trade at a specified price or better: a buy cannot execute above its limit, and a sell cannot execute below its limit. Partial fill Partial fill is the execution of fewer shares than an order requests, leaving a remaining quantity that may stay open or be canceled under the order’s conditions. Gap risk Gap risk is the possibility that a stock’s next available trading price jumps above or below its previous price, causing a fill or loss beyond the level expected. Time in force Time in force is an order instruction that specifies how long an order remains eligible for execution before it expires or is canceled. Bid-ask spread Bid-ask spread is the difference between the lowest displayed price to sell a stock (ask) and the highest displayed price to buy it (bid), measured per share.

Execution & trading costs

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Educational content, not investment advice. PreTrAIde is analysis software, not a broker: it never executes orders, and its verdicts are decision support, not recommendations to buy or sell.