Why a Gold Limit Order Can Fill Only One Contract

Identify the matching rule

On an exchange order book, a resting buy limit specifies the highest price the buyer will pay. Other buyers may already be bidding at that price. The venue’s allocation rule determines how incoming sell quantity is divided among eligible resting buyers. The displayed last trade records a price and quantity from a match. It cannot by itself identify which account received the fill.

CME’s FAQ for the Gold (Enhanced Delivery) futures contract, code 4GC, lists first-in, first-out matching. That gives us a concrete gold example. CME also documents other allocation methods across its markets. Confirm the product and order type on the ticket before applying a simple queue example to a spread, a different exchange product or a bilateral broker quote.

Source notes: [1] CME Group — FAQ: Gold (Enhanced Delivery) futures · [2] CME Group — Matching Algorithm Overview

Walk four contracts through the queue

In a hypothetical first-in, first-out book, suppose seven contracts bid at your price have priority when your buy order for four contracts is acknowledged. Freeze every other variable. An incoming seller executes five contracts at that price. Two contracts still stand ahead of you and all four of yours remain open. The first trade at your limit has given you zero exposure.

A second seller executes three contracts at the same level. Two go to the earlier buyers and one goes to you. Your position is now long one contract, with three resting. If those remaining orders stay working and another seller arrives, your exposure may grow without another click. If some of the original seven had cancelled before the first match, the sequence would be different. These assumptions are explicit because the arithmetic depends on them.

Reconcile after a cancel request

Imagine requesting cancellation of the remaining three while another contract is being matched. A cancellation request expresses your intention. Read the acknowledgement and execution reports to learn what actually happened. One possible final record is two bought, two cancelled and zero left working. Another is one bought, three cancelled and zero working. The difference matters when attaching an exit.

I reconcile original quantity as cumulative filled plus confirmed cancelled plus still working, accounting separately for amendments. For each execution I keep order ID, fill ID, quantity, price and exchange timestamp if provided. If two fills have different prices, their quantity-weighted average is the relevant entry for the combined position. Unfilled contracts do not enter the average.

Choose evidence that matches the question

A candle that reaches a level has no field for your queue position. CME distinguishes its aggregated Market by Price feed from its order-level Market by Order feed, which can support queue analysis. A replay built from candles alone should label its assumed fill policy and test a less favorable alternative. For the actual order, start with the account’s fill reports. They establish your executed quantity even when the chart cannot explain every change in the queue.

Source notes: [3] CME Group — Market by Order FAQ