Order Types & Time in Force

Understanding how to construct and control your orders is fundamental to trading effectively on ElectronX. This guide covers the two order types available on the platform, the five Time in Force (TiF) designations that control how long your orders remain active, and the Top of Book (ToB) toggle that enables Market-Limit behavior.

Order types

Limit Order

A limit order is an instruction to buy or sell a contract at a specific price or better. The order will only execute at your stated price or at a more favorable price, never worse. If the market is not at your price, the order rests in the order book and waits.

Limit orders give you full price control, but they do not guarantee execution. If the market never reaches your limit price before the order expires, it will not fill.

Use a limit order when: you have a specific price target, you are providing liquidity to the market, or you want protection against unexpected price movements. ElectronX supports limit orders across most order entry methods, with Market-Limit orders available exclusively for top-of-book execution.

Market-Limit Order

A market-limit order is an instruction to buy or sell a contract immediately at the best available price, up to your stated limit. The order attempts to execute against the best available counterparty at the moment of submission; any quantity that does not fill immediately rests in the order book as a limit order at your stated price. A market-limit order will never execute at a price worse than your limit.

Use a market-limit order when: immediate execution is the priority and you want price protection on any unfilled quantity.

The Top of Book (ToB) toggle

The ToB checkbox in the ElectronX trading interface enables a Market-Limit order.

When ToB is checked, your order first attempts to execute immediately at the best available market price. Any quantity that does not fill immediately converts to a limit order at the price you specified, and rests in the order book for the remainder of the order's time in force.

This gives you immediate execution against available liquidity while protecting the unfilled portion against prices beyond your stated limit.

To place a Market-Limit order: check the ToB (Top of Book) checkbox in the order entry panel before submitting.

Time in Force designations

Time in Force controls how long an order remains active. You select a TiF at order submission; it cannot be changed after the fact except through Cancel-Replace.

DAY

A DAY order is valid for the current trading session only. Any unfilled quantity is automatically canceled when the market closes at 9:00 PM CT (ERCOT).

Use DAY when: you want intraday exposure without the order carrying forward overnight.

GTC — Good Till Canceled

A GTC order remains active until it is completely filled or you explicitly cancel it. GTC orders persist across trading sessions and will continue working day after day until they execute, you cancel them, or the contract expires.

Use GTC when: you are willing to wait across multiple sessions for a specific price.

GTD — Good Till Date

A GTD order allows you to specify a precise expiration date and time. The Matching Engine will automatically cancel the order at your chosen time if it has not been fully filled.

• Via the GUI: enter the expiration date and time in your local time zone, or select from a pre-defined menu of relative expiration options.
• Via FIX API: the expiration time must be a UTC timestamp set explicitly — no relative-time options are available via API.

Changing a resting order's TiF to or from GTD via Cancel-Replace does not affect its queue position.

Use GTD when: you want an order to expire at a specific time — for example, before a scheduled news event, before a contract's hourly expiration, or at end of day for a non-DAY session.

IOC — Immediate or Cancel

An IOC order seeks immediate execution of as much of the order as possible. Any portion that cannot be filled at the moment of submission is automatically canceled — no resting order is left in the book.

IOC allows partial fills: if 7 of your 10 requested lots are available at the market, you will receive 7 and the remaining 3 will be canceled.

Use IOC when: you want to capture immediately available liquidity without leaving an open order in the market.

FOK — Fill or Kill

An FOK order must be executed in its entirety, immediately, or not at all. Unlike IOC, FOK does not permit partial fills. If the full quantity cannot be filled at the specified price or better at the moment of submission, the entire order is canceled.

Use FOK when: you need to execute a complete block in one shot — for example, a risk hedge that only makes sense if the full quantity fills simultaneously.

TiF comparison

TiF	Partial fills?	Rests in book?	Expires when?
DAY	Yes	Yes	Market close
GTC	Yes	Yes	When you cancel it (or contract expires)
GTD	Yes	Yes	At your specified date/time (or contract expires)
IOC	Yes	No	Immediately (unfilled portion)
FOK	No	No	Immediately (if full fill unavailable)

What cannot be changed after submission

Once an order is submitted, the following attributes cannot be modified even through Cancel-Replace: the contract (product, instrument, and expiration), the side (buy or sell), the order type (limit or market), and the trading account. Price, quantity, and TiF can be modified.

Notes

Self-Match Prevention rules apply to all order types: you cannot simultaneously hold a resting bid and a resting offer at the same price in the same contract.