Order modification (cancel/replace)
Order modification is changing a working order's price or quantity after it was accepted, either through a native modify message or by canceling it and sending a new one. The change can cost the order its place in the queue, and while it is in flight the old order can still fill.
Senzoukria · Glossary · Updated September 2026
Modify versus cancel and replace
A native modification changes an existing order in place and keeps its identifier. A cancel/replace removes the order and sends a new one, which is a new arrival in every respect. Some brokers and gateways implement what the platform calls a modification as a cancel/replace, which is why an order's identifier can change after a simple price move.
What happens to queue priority
On price-time priority markets, time priority is tied to the order's arrival at its price. On CME Globex, increasing an order's quantity or changing its price costs its time priority, while reducing its quantity keeps its place. A price change is in any case a new place in a different queue. Exchange rules are the reference for edge cases such as account or display-quantity changes.
| Change | Queue position afterwards |
|---|---|
| Reduce quantity | Kept |
| Increase quantity | Lost: back of the queue at the same price |
| Change price | Back of the queue at the new price |
| Cancel and send a new order | Back of the queue as a new order |
A worked example
A trader placed a bid for 5 contracts at 4,995.00 early, with 120 contracts ahead. Since then 380 contracts have joined behind. Reducing the order to 3 keeps its place, 120 contracts from the front. Increasing it to 8 sends it behind the 380 newcomers, 500 contracts from the front: a larger order that is now much less likely to fill before the level trades through.
The race with fills
- A modification is a request. Until the broker confirms it, the old order is live and can fill at its old price.
- With a cancel/replace, a fill of the old order and the arrival of the new one can both happen, briefly doubling the intended size.
- After any modification in a fast market, read the working orders and the position again rather than assuming the new state.
In Senzoukria
Every working order is drawn on the chart as a line with its side, type, remaining quantity and price. Dragging an order line moves that order to the dropped price and restates its original order type; the modification is sent after 350 milliseconds of stillness or on mouse release. While the gesture or the modification is in flight, reconciliation leaves the line where you put it, so the next market update does not drag it back mid-gesture. When a broker modifies by cancel and recreate, the order identifier changes and the line is rebuilt from the new order. Refusals are shown as a notice over the chart with the gateway's message.
Related
In the same section
- Order routing
- Order guardrails
- Order ticket
- Order flow toxicity
- Other-timeframe participant
- Order flow software
- Out of the money
- Order flow
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Frequently asked questions
- Does moving my limit order by one tick keep its priority?
- No. A price change places the order at the back of the queue at its new price, behind everything already resting there. If the aim is to keep priority, the only change that preserves it on CME is a reduction of quantity.
- Is a modification the same as cancel and replace?
- Not always. A native modification keeps the order's identifier, while a cancel/replace creates a new order. Both can lose priority depending on what changed. The practical difference is the in-flight window: with cancel/replace, two orders can exist or fill around the same moment.