How to use Post-Only order settings? (Maker fee optimization)

Understanding Post-Only Order Mechanics

1. A Post-Only order is designed to ensure that the trade is added to the order book and never executes immediately against an existing counter-order.

2. If a Post-Only order would match with an order already present on the opposite side of the book, the exchange rejects it instead of filling it as a taker trade.

3. This behavior guarantees the trader retains maker status, which qualifies them for lower or even negative fees depending on the platform’s fee schedule.

4. The order must be placed at a price strictly better than the best available bid or ask—meaning buy orders must be below the top ask, and sell orders must be above the top bid.

5. Some exchanges enforce this via a “price improvement” check before order acceptance, while others apply stricter rounding or tick-size alignment rules.

Platform-Specific Implementation Variations

1. Binance applies Post-Only logic only to limit orders and disables it for market or stop-limit orders entirely.

2. Bybit allows Post-Only on both linear and inverse perpetual contracts but enforces stricter latency-aware validation during high volatility periods.

3. OKX requires users to manually toggle the Post-Only flag in advanced order settings and displays a real-time warning if the entered price violates the condition.

4. Kraken uses the term “post-only” interchangeably with “limit-only” in its API documentation but enforces identical matching semantics across spot and margin markets.

5. Coinbase Pro does not expose Post-Only as a standalone option; instead, it embeds the logic into its “Limit GTC” order type with implicit rejection on immediate fill.

Fee Implications and Arbitrage Considerations

1. Maker fees on major exchanges range from 0.02% to −0.01%, meaning some platforms pay rebates for adding liquidity.

2. Taker fees typically sit between 0.04% and 0.10%, creating a direct cost delta of up to 0.11% per executed trade.

3. High-frequency market makers rely on Post-Only settings to sustain profitability when spread compression reduces per-trade revenue.

4. Arbitrageurs use Post-Only orders across correlated assets—such as BTC/USDT and BTC/USD—to lock in cross-exchange spreads without triggering taker fees on both legs.

5. During flash crashes, Post-Only orders may fail silently, leading to missed opportunities unless paired with fallback logic like IOC or Reduce-Only variants.

Risk Factors and Common Pitfalls

1. Price slippage can occur when rapid order book shifts cause a previously valid Post-Only price to become aggressive due to top-of-book movement.

2. Order rejection rates increase significantly during low-liquidity hours, especially on altcoin pairs where bid-ask depth is shallow.

3. Some exchanges do not refund the fee associated with rejected Post-Only orders, treating the submission itself as a chargeable API event.

4. Traders using automated strategies must account for network latency—what appears as a valid price locally may already be outdated upon server receipt.

5. Misconfigured trailing-stop or conditional orders may inadvertently trigger Post-Only enforcement when underlying price conditions shift unexpectedly.

Frequently Asked Questions

Q: Does Post-Only guarantee my order will remain on the book indefinitely?No. It only guarantees non-execution upon placement. Once placed, the order behaves like any other limit order and may be filled later when matching occurs.

Q: Can I combine Post-Only with time-in-force modifiers like GTD or FOK?Most exchanges restrict Post-Only to GTC or IOC types. GTD is rarely supported, and FOK contradicts Post-Only logic by design.

Q: Why did my Post-Only buy order execute instantly despite being priced below the ask?This usually indicates the displayed ask was stale or the exchange applied price-tiered rounding—your submitted price was internally adjusted upward past the best ask.

Q: Do decentralized exchanges support Post-Only semantics?Native Post-Only is rare on AMM-based DEXs like Uniswap, but order-book protocols such as dYdX and DeversiFi implement full Post-Only compliance with on-chain validation.