What is a post-only order in futures?

Understanding the Concept of a Post-Only Order

A post-only order is a specialized type of limit order used in cryptocurrency futures trading. This order ensures that the trade will only be executed if it does not immediately match with an existing order on the opposite side of the market. In other words, the post-only order must add liquidity to the order book, rather than remove it. If the order would otherwise result in an immediate execution (i.e., matching with a resting order), it gets canceled automatically.

This feature makes post-only orders particularly useful for traders who want to avoid paying taker fees and instead benefit from maker rebates offered by many exchanges. The essence of this order lies in its ability to maintain the trader's position on the order book without triggering instant trades.

How Does a Post-Only Order Work?

When placing a post-only order, the system checks whether the order can be placed on the order book without being filled immediately. If the bid price is higher than or equal to the best ask price (for buy orders), or the ask price is lower than or equal to the best bid price (for sell orders), the order will not be accepted and will be canceled.

For example:

• If you place a buy post-only order at $30,000 when the current best ask is $29,500, the order will execute immediately as a taker order — hence, it will be rejected.
• However, if you place a buy post-only order at $29,400 when the best ask is $29,500, it will be added to the order book as a maker order, waiting for a seller to match it later.

This mechanism enforces the rule that post-only orders cannot act as taker orders under any circumstances.

Why Use a Post-Only Order in Futures Trading?

Traders often use post-only orders to optimize their trading costs. Since these orders are classified as maker orders, they typically qualify for lower fees or even fee rebates depending on the exchange's fee structure.

Additionally:

• They help traders avoid slippage by ensuring that their orders don't get filled at less favorable prices due to aggressive market conditions.
• They allow traders to set up limit orders with confidence that those orders won’t accidentally execute immediately at undesirable levels.
• They are commonly used in algorithmic trading strategies where maintaining a presence in the order book is more important than immediate execution.

By using post-only orders, traders gain more control over execution quality and cost efficiency.

Differences Between Post-Only Orders and Other Order Types

It's essential to distinguish post-only orders from other common order types like market orders, standard limit orders, and immediate-or-cancel (IOC) orders.

• Market Orders: Execute instantly at the best available price but do not go into the order book. They always act as takers.
• Standard Limit Orders: Can either act as makers or takers depending on the market price. They may get filled immediately if placed at or better than the current market price.
• Immediate-or-Cancel (IOC): Executes immediately any portion that can be matched and cancels the rest. These also act as takers.

In contrast, a post-only order strictly functions as a maker and never executes immediately. If it would otherwise act as a taker, it gets canceled entirely.

Setting Up a Post-Only Order: A Step-by-Step Guide

Placing a post-only order varies slightly across platforms, but most major exchanges like Binance, Bybit, and OKX support this functionality. Below is a general guide applicable to most futures trading platforms:

• Navigate to the trading interface for the desired futures contract.
• Select 'Limit Order' as the order type.
• Look for the option labeled 'Post-Only,' usually found near advanced order settings.
• Enable the post-only checkbox or toggle switch.
• Enter your desired price and quantity for the order.
• Review the order details carefully to ensure it aligns with your strategy.
• Click 'Buy' or 'Sell' to submit the order to the exchange.

Some exchanges may display a warning if your price setting would trigger an immediate fill, prompting you to adjust the price before proceeding.

Common Scenarios Where Post-Only Orders Are Beneficial

There are several situations where using a post-only order becomes strategically advantageous:

• When trying to accumulate a large position gradually without moving the market price.
• In arbitrage setups where orders need to sit in the book until price discrepancies arise.
• During high volatility periods, where traders wish to avoid accidental fills at unfavorable prices.
• For users participating in maker rebate programs offered by exchanges to reduce overall trading costs.

These scenarios highlight how post-only orders offer precision and control, especially in fast-moving futures markets.

Frequently Asked Questions

Q1: Can I convert a regular limit order into a post-only order after submission?No, once a limit order has been submitted, it cannot be changed to a post-only order. You must cancel the existing order and resubmit it with the post-only option enabled.

Q2: Do all exchanges support post-only orders in futures trading?Most major cryptocurrency exchanges do support post-only orders for futures contracts. However, availability may vary depending on the specific platform and the trading pair or contract involved.

Q3: What happens if my post-only order partially matches with another order?A post-only order cannot be partially filled if doing so would result in a taker trade. The entire order must either be fully added to the order book or canceled if it would otherwise match immediately.

Q4: Is there a minimum time a post-only order must remain in the book before being canceled?Generally, no. As long as the post-only order does not match with existing orders upon submission, it will remain in the book indefinitely until filled or manually canceled by the user.