How to use post-only orders for a crypto contract? (Fee Saving)

Understanding Post-Only Orders in Crypto Derivatives

1. A post-only order is a type of limit order that executes exclusively as a maker — meaning it must rest on the order book and cannot match against an existing order immediately.

2. If a post-only order would execute against a resting order upon submission, the exchange rejects it instead of filling it as a taker.

3. This mechanism ensures the trader receives the maker fee rebate rather than paying the higher taker fee.

4. Most major crypto derivatives platforms — including Binance Futures, Bybit, OKX, and BitMEX — support post-only orders for perpetual and quarterly contracts.

5. Traders often deploy post-only orders when placing aggressive limit orders near the top of the order book to avoid accidental taker execution during volatile price movements.

How Post-Only Orders Reduce Trading Fees

1. Maker fees on crypto futures exchanges typically range from -0.01% to 0.02%, while taker fees range from 0.04% to 0.075%.

2. A post-only order guarantees the lower (or negative) maker rate even if the market moves rapidly toward the limit price.

3. For high-frequency scalpers or arbitrageurs, saving even 0.03% per trade compounds significantly across thousands of executions daily.

4. Some exchanges apply tiered fee structures — using post-only consistently can help maintain higher VIP levels by increasing maker volume contribution.

5. Fee rebates from post-only activity are credited instantly upon order placement and full or partial fill, visible in real-time balance updates.

Implementation Across Major Platforms

1. On Binance Futures, traders enable post-only via the “Post Only” checkbox in the advanced order panel or by appending postOnly=true in API requests.

2. Bybit requires setting order_type=Limit and time_in_force=PostOnly in REST or WebSocket API calls; UI users toggle “Post Only” below the price input field.

3. OKX supports post-only through both web interface toggles and API parameter posSide=net combined with ordType=limit and reduceOnly=false.

4. BitMEX uses the execInst=ParticipateDoNotInitiate flag in its legacy API to enforce post-only behavior.

5. Failure to set correct parameters may result in silent rejection or fallback to standard limit order logic — always verify response codes and order status logs.

Risks and Limitations of Post-Only Execution

1. Rejection risk increases during low-liquidity periods — if no space exists on the order book at the specified price, the order fails entirely.

2. Slippage is not applicable since no execution occurs, but opportunity cost accumulates when price moves past the limit without fill.

3. Some exchanges impose minimum order size thresholds for post-only eligibility — e.g., 0.001 BTC on certain perpetual pairs.

4. Post-only orders cannot be used with stop-market, stop-limit, or trailing stop triggers — they are strictly for passive limit entry or exit.

5. In fast-moving markets, repeated re-submission of rejected post-only orders may trigger rate-limiting penalties or temporary API bans.

Frequently Asked Questions

Q: Can I cancel a post-only order after submission?Yes. Post-only orders behave like standard limit orders once placed — cancellation is permitted at any time before matching.

Q: Does post-only affect leverage or margin requirements?No. Margin calculation remains identical to regular limit orders — only fee classification changes.

Q: Why did my post-only order disappear without filling or rejecting?This usually indicates exchange-side timeout or internal validation failure — check API response headers for HTTP 400 or 429 status codes.

Q: Is post-only available for all contract types on a given exchange?Not universally. Certain exotic instruments — such as MOVE contracts or options — may exclude post-only functionality entirely.