Understanding Post-Only Orders: How to Lock in Lower Trading Fees

If you trade frequently or manage large positions, you’ve probably noticed that trading fees can significantly impact your bottom line. One powerful tool that can help you take control of these costs is a post-only order. When you use this feature with your limit orders, you guarantee that your orders will enter the order book rather than being executed immediately as a market order—and this distinction makes a real difference in what you ultimately pay.

What Are Post Limit Orders and Why They Matter for Fee Control

A post-only order is an optional feature you can attach to your limit or conditional limit orders. Here’s the core idea: the system will automatically reject your limit order if it detects that the order would execute immediately upon placement. In other words, your order is guaranteed to be placed into the order book, not filled right away against existing market orders.

Why does this matter? Because the order book placement determines your fee structure. Orders that rest in the order book qualify for the lower maker fee, while orders that are immediately matched against existing liquidity incur the higher taker fee. For high-volume traders, scalpers, and anyone managing large positions, this fee difference can compound into substantial savings over time.

The post-only order feature is available across multiple trading environments: it works with Spot Trading (for Unified Trading Account users) and with Perpetual & Futures Trading (for both Standard and Unified Trading Account users), giving you flexibility across your entire trading strategy.

The Fee Advantage: Maker vs Taker Fees Explained

To understand why the post-only order option is so valuable, consider the fee structure. When your order rests passively in the order book and waits for a match, you pay the maker fee—typically the lower rate. When your order is immediately matched against existing orders, you pay the taker fee—typically higher.

Without intentional control, you might expect to pay a maker fee but accidentally trigger a taker fee instead. This can happen in fast-moving markets where prices shift between the moment you submit your order and the moment it’s placed into the system. Without the post-only protection, the system will automatically execute your limit order as if it were a market order, filling it from the best available prices until your full order is satisfied. That unintended market execution means paying the higher taker fee when you’d budgeted for the lower maker fee.

It’s worth noting that the final execution of your limit order also depends on the Time-In-Force strategy you select (such as GTC, IOC, or FOK), which controls how long your order remains active. Post-only orders work in concert with these settings to give you the fee control you’re seeking.

Real-World Scenario: How Post-Only Orders Protect Your Trading Costs

Imagine a rapidly falling market. You place a buy order for 100,000 BTCUSD contracts at USD 9,000. When you first glance at the order book, the best ask price is USD 9,001—slightly above your limit. But by the time your order is submitted, the market has moved and the best ask is now USD 8,995.

Without the post-only option: Since the best ask price (USD 8,995) is now better than your limit price (USD 9,000), the system treats your limit order as a market order. It fills your entire position from USD 8,995 up to your limit of USD 9,000. The result? You unintentionally paid the taker fee instead of the maker fee you expected.

With the post-only option enabled: The system detects that your order would execute immediately and automatically cancels it rather than placing it into the order book. You don’t get filled, but more importantly, you avoid paying that unexpected taker fee. You remain in control of your costs.

Maximize Trading Efficiency Across Your Accounts

The post-only order feature gives you a straightforward way to align your order placement with your fee expectations. Large-volume traders especially benefit, since the savings accumulate across hundreds or thousands of trades. By strategically using post-only orders with your limit orders, you maintain tighter control over whether you pay maker or taker fees—and that control is especially valuable in volatile markets where prices move rapidly between order submission and execution.