Order types and order matching

Wednesday 14 October 2026, 08:29:59 ET (Eastern Time, New York; 19:29 ICT, Vietnam time during US summer time). NQ futures last traded at 30,839.75; 08:30 ET is when scheduled US economic reports come out. At 08:30:01.286 a burst of selling printed from 30,835.25 down to 30,775.25 in one millisecond. Then nothing traded for five seconds. The next trade was 30,725.00.

A trader long (vị thế mua, profiting if price rises; short is vị thế bán, profiting if price falls) with a sell stop at 30,770.00 had planned to lose 30 points. Nothing traded between 30,775.25 and 30,725.00, so the loss was at least 75 points.

This lesson answers two questions. What does each order type actually promise? And when many orders want the same price, which ones does the exchange fill first?

Key terms

• Bid and ask (giá mua / giá bán): the best prices buyers and sellers are waiting at. The gap between them is the spread (chênh lệch giá) Definition.
• Tick (bước giá): the smallest price step. On NQ it is 0.25 points ($5 per contract); on the micro MNQ (Micro E-mini Nasdaq-100, $2 per point), $0.50 Definition.
• Resting order (lệnh chờ): a limit order waiting in the book until someone trades against it; it provides liquidity. An order that trades at once takes liquidity: it is the aggressor Definition.
• Slippage (trượt giá): the distance between the price you planned and the fill price you got Definition.
• Queue (hàng đợi): all the resting orders at one price, in the order they arrived Definition.
• Price-time priority (ưu tiên giá rồi đến thời gian), also called FIFO (first in, first out): the better price fills first; at the same price, the earlier order fills first Definition.

Chart first: one price, one line of orders

How it works

Every order trades price against certainty

No order type gives you both a sure fill and a sure price. Pick the one that matches what you intend to do Definition.

• Market order (lệnh thị trường): fill now at whatever price is available. Sure to trade, not sure of the price.
• Limit order (lệnh giới hạn): fill only at your price or better. Sure of the price, not sure to trade. A missed fill is a limit order’s honest outcome, not a malfunction.
• Stop-market order (lệnh dừng): waits until the market trades at your stop price, then becomes a market order. It is the usual exit for “my idea is wrong”. It promises the trigger, not your price.
• Stop-limit order: the trigger sends a limit order instead. It caps your price and can leave you holding the position if the market jumps past your limit.
• Bracket and OCO (one-cancels-other): an entry sent with a stop and a target; when one exit fills, the other is cancelled (MKT2.06).
• Time in force: a DAY order expires at the session’s end; a GTC (good-til-cancelled) order stays until filled or cancelled. Review working orders like positions.

Where your stop lives also matters. CME attaches a protection limit to market and stop orders it holds: they fill only within a set number of points of the trigger, and the rest waits as a limit. Some brokers and platforms hold the stop on their own server, or on your computer, and send a market order when it triggers Definition. Ask your broker which you have.

How Globex decides who gets filled

CME Globex is the exchange’s matching engine (bộ khớp lệnh). For ES and NQ outright futures it uses pure FIFO: best price first, then the earliest order at that price Definition. Some other CME products use pro-rata rules (fills shared by order size), so do not assume FIFO everywhere.

Two consequences cost beginners money:

1. Changing a resting order’s price, or raising its size, sends it to the back of the queue. Reducing its size keeps your place Definition.
2. Your place in line decides whether a good price pays you. The lots ahead of you can absorb all the selling at your level.

What the queue can tell you, and what it cannot

Queue imbalance (mất cân bằng hàng đợi) compares the sizes at the best bid and ask: (bid size − ask size) ÷ (bid size + ask size). With 60 lots bid and 20 offered it is +0.5 Definition. The thinner side tends to give way first, so the next tick is more often up when the bid is heavier: measured in peer-reviewed research on 10 liquid Nasdaq stocks (MeasuredOther market, extrapolated to NQ as PlausibleOther market) and reported on NQ in a public practitioner study PlausibleOne trader's study.

The catch is size. If the next one-tick move goes your way 65.6% of the time (15.6 percentage points, or pp, above a 50% coin flip), your average gain is (0.656 − 0.344) × 1 tick, about 0.3 of a tick. A market order pays the spread, at least one tick, before fees. So queue imbalance cannot pay for a market-order entry. It can help time a limit order: when your side of the book is the thin one, a fill is more likely, and so is a next tick against you.

Why it is still worth knowing

Order types and FIFO rules are exchange mechanics Definition, not a directional signal. They still decide three things on every trade: whether a fast release can skip your limit price, whether modifying a resting order forfeits your queue priority, and why a one-tick order-book edge is for passive execution rather than market orders.

What the data says

Worked example: a long on a real tape

The tape is real (NQ trades from our lab’s tick record, 14 October 2026); the position is an illustration.

Suppose you bought one MNQ at 30,800.00 shortly after 08:00 ET (NQ traded 30,758.75 to 30,852.75 from 08:00 to 08:30). You are wrong below 30,770.00: 30 points of risk, $60 on MNQ ($600 on NQ).

• Sell stop-market at 30,770.00. The burst stopped at 30,775.25. After the silence the first trade was 30,725.00, the first price your stop could fill: at least 45 points of slippage (180 ticks), a loss of at least 75 points, $150 on MNQ ($1,500 on NQ). Held at CME with a protection limit above 30,725.00, part of it could have waited unfilled instead.
• Sell stop-limit at 30,770.00, limit 30,768.00. It triggers on the 30,725.00 trade, then waits for a buyer at 30,768.00 or better. None comes. At 08:31:18 ET NQ traded 30,620.25: you are still long, 179.75 points down, $359.50 on MNQ ($3,595 on NQ).

Decide which risk you accept before the release, not during it. A five-second pause like this is what CME’s velocity logic produces when price moves too far too fast (MKT1.05); we have not matched it to CME’s records.

The mirror and the failure

Short side. On Friday 23 October 2026 NQ’s last trade before the weekend was 29,175.00 at 16:59:59 ET (03:59 ICT Saturday). Suppose you were short one MNQ from 29,170.00 with a buy stop at 29,200.00. The market reopened on Sunday 25 October at 18:00 ET (05:00 ICT Monday) with a first trade at 29,268.00. The stop could fill no lower: 68 points of slippage, a loss of at least 98 points, $196 on MNQ ($1,960 on NQ).

The failure of a good limit. Picture the chart’s queue on another day. Your bid at 30,800.00 is the right level: the dip stops there and the market rallies 40 points. But 38 lots were ahead of you and only 25 traded at 30,800.00. Price-time priority ignores your analysis. Join earlier, or accept that a limit sometimes misses.

Do it on the platform

Our desk sends orders from TopstepX and reads order flow in ATAS X on a second screen.

Prop-firm note. Evaluation accounts fill your orders in a simulator, which cannot know your real place in a queue. Firms treat strategies that exploit simulated fills as prohibited conduct; the Prop Firm course (PROP1.04) will quote the rule with its date once we have checked it.

Common mistakes

Common mistake: nudging a resting limit one tick to “improve” it. The change makes it a new order at the back of the line; price touches your old level, fills everyone who stayed, and leaves without you.

Common mistake: treating queue imbalance as a direction signal. A heavy bid points to the next tick, not the next ten points. A rate above 50% is not an edge until it beats its costs.

Drill: trace your place in the queue

You rest a 1-lot buy limit on MNQ at 30,800.00 when 25 lots are already resting at that price.

1. Twelve new lots join at 30,800.00, 6 lots ahead of you cancel, and a 15-lot sell market order hits 30,800.00. How many lots are still ahead of you?
2. You move your order down to 30,799.75 and then back to 30,800.00 while 18 lots are resting at 30,800.00. How many lots are ahead of you now?

Recap

• A market order makes the trade sure, a limit order the price, a stop the exit trigger. None makes both price and fill sure.
• In a jump, a stop-market fills at the first price traded past it; a stop-limit can leave you in the position. On 14 October 2026 the first slipped 45 points; the second stayed open while NQ fell about 105 more.
• ES and NQ outrights fill by price, then by time. Changing a resting order’s price or raising its size sends it to the back.
• Queue imbalance points to the next tick with an effect below one tick (one practitioner’s NQ study): use it to time limit orders, not to send market orders.

Further reading

• CME Group, CME Globex matching algorithms, product by product.
• CME Group, iLink order cancel-replace: which changes cost your queue place.
• CME Group, Protection functionality for market and stop orders.
• Gould and Bonart, Queue imbalance as a one-tick-ahead price predictor (10 Nasdaq stocks).
• Order Flow, Measured: all claims, row MR-06.
• Topstep help center, order types, fills and slippage.
• Our lab: on 11 September and 14 October 2026 NQ’s 08:30 ET tape shows a burst, five seconds without a trade, and a reopen 47 and 50.25 points lower. How often this happens is not yet measured.

Prerequisites and next

Read M0.01 (spread and adverse selection) and M0.02 (bid, ask, tick, aggressor) first. Next: M0.04 puts 08:30 ET and the other session times on your clock in ET and ICT, so you know when jumps like these are scheduled. Deeper: MKT2.01, MKT2.02 and M3.08.

Educational content only. Not financial advice. Futures trading involves substantial risk of loss. Not affiliated with Topstep; firm rules change; check the Topstep help center.