How an order queue ranks resting orders for execution, including price-time priority, queue position, partial fills, and venue-specific rules.
An order queue is the ranked set of orders waiting to trade at a particular price on a trading venue. The venue’s matching rules determine which eligible order receives the next execution. In a price-time market, a better price ranks first and an earlier order generally ranks ahead of a later order at the same price.
Consider the buy side of a limit order book. A bid at $25.01 normally has price priority over bids at $25.00. If several eligible bids rest at $25.01, the venue applies its allocation rule to decide which one trades first when a matching sell order arrives.
Under simple first-in, first-out price-time priority:
Nasdaq’s U.S. equity market, for example, describes a price-time model in which displayed limit orders at the same price execute in receipt order, while non-displayed shares rank after displayed shares at that price. Other markets can use different priority models, especially in listed derivatives.
| Priority model | Basic allocation | What it means for the queue |
|---|---|---|
| Price-time | Best price first, then earliest eligible order | Joining an existing price level usually places a new order behind earlier orders |
| Pro rata | Best price first, then allocation partly by displayed or eligible size | A later large order may receive part of an execution before an earlier order is fully filled |
| Customer priority | A specified customer class ranks ahead of other participant classes at the same price | Timestamp alone does not determine the entire queue |
| Display priority | Displayed interest ranks before non-displayed interest at the same price | Hidden liquidity may execute only after displayed orders |
| Auction allocation | Venue-specific rules combine price, imbalance, time, size, or other factors | Continuous-market queue assumptions may not apply at the open or close |
The applicable exchange rulebook and order-type specification control. A platform’s depth display is not a substitute for those rules.
| Concept | Main question answered | Typical view |
|---|---|---|
| Order queue | Which eligible order at one price is next? | Priority within a price level |
| Order Book | Where are current bids and offers? | Multiple price levels on both sides |
| Market Depth | How much visible size is available across prices? | Aggregated quantities by price level |
| Trade tape | What transactions have completed? | Price, size, time, and available trade conditions |
Assume a venue uses strict price-time priority and has three displayed buy orders at $40.00:
| Queue rank | Order | Remaining shares |
|---|---|---|
| 1 | Order A | 300 |
| 2 | Order B | 400 |
| 3 | Your order | 500 |
An incoming sell order for 600 shares reaches the venue at $40.00. Order A receives 300 shares, and Order B receives the next 300. Order B still has 100 shares ahead of your order, so your order receives no fill.
If another eligible sell order for 250 shares arrives before the queue changes, the remaining 100 shares of Order B trade first and your order receives a 150-share partial fill. Your remaining quantity is 350 shares.
This example assumes one venue, displayed orders, no special participant priority, and no cancellations or modifications. In a live market, orders may be added, canceled, hidden, routed elsewhere, or processed under a different allocation model.
A resting limit order is the clearest example. It specifies a worst acceptable price and can wait on the book if it does not execute immediately.
A market order generally removes available liquidity immediately and therefore should not be described as a standing market-price queue. A stop order is normally held or inactive until its stop price is reached; after activation, it becomes the order type specified in its terms. Pegged, reserve, midpoint, post-only, and discretionary orders can receive specialized handling.
Queue position can change when:
Reducing an order’s quantity may preserve priority on some venues, while increasing size or changing price may create a new timestamp. Do not generalize one exchange’s rule to another venue or product.
Identify the venue, product, session, order type, display status, and allocation algorithm. Check whether the data is direct or consolidated, how much depth it includes, and whether timestamps reflect exchange receipt or local display time. For execution analysis, compare the original order record with acknowledgments, modifications, partial fills, cancellations, and the prevailing quotes.
Queue analysis is most reliable when tied to a specific order and venue rule. A screenshot without a timestamp, venue, and feed description is weak evidence.
This article is educational and does not provide personalized trading, investment, or legal advice. Actual execution is governed by the broker’s handling and the applicable venue rules.