What is "Post-Only" order in contracts? (Maker Strategy)

Core Mechanics of Post-Only Execution

1. A Post-Only order is a strict limit order that must be placed at a price that does not cross the current spread. It cannot match immediately against any existing counterparty order in the order book.

2. The exchange performs real-time validation: if the bid price is greater than or equal to the best ask, or the ask price is less than or equal to the best bid, the order is rejected outright with no ID assigned.

3. Only when the bid sits strictly below the best ask and the ask sits strictly above the best bid does the order enter the order book as a visible liquidity provision.

4. This mechanism guarantees the trader assumes the role of a Maker—never a Taker—regardless of subsequent market movement during order placement.

5. No partial fills are permitted under Post-Only logic; the entire order either posts successfully or fails entirely.

Fee Implications and Economic Incentives

1. Exchanges apply differentiated fee schedules: Maker fees are consistently lower than Taker fees, often by a factor of two to five across major derivatives platforms.

2. Certain venues offer negative maker fees, meaning users receive rebates upon execution—effectively earning income for providing liquidity.

3. On perpetual swap markets, the cumulative savings from avoiding Taker fees can exceed 0.03% per round-turn trade, scaling non-linearly with position size and frequency.

4. Arbitrageurs and market makers rely on this structural asymmetry to sustain low-margin, high-volume operations without erosion from frictional costs.

5. Fee differentials directly influence order routing decisions, especially among co-located algorithmic systems competing for queue priority in the top-of-book layers.

Interface Implementation Across Major Platforms

1. OKX displays a toggle labeled “PO” inside its advanced order panel; activation requires explicit user confirmation before submission.

2. Bybit integrates Post-Only as a default option within its “Limit” dropdown, but only activates it when the “Maker Only” checkbox is manually enabled.

3. Hyperliquid embeds Post-Only behavior into its native order type selection, where “Limit (PO)” appears as a distinct entry separate from standard limit orders.

4. BitTap surfaces a dynamic “Set as Passive” button after price input, which visually confirms activation via a persistent green “PO” badge beside the order preview.

5. Deribit requires users to select “Post Only” from a dedicated order-type menu—no fallback to standard limit logic occurs if misconfigured.

Operational Risks and Failure Modes

1. Price precision errors cause silent rejection: submitting 100.00 when best ask is 100.00 triggers immediate rejection even though human perception treats them as identical.

2. Network latency spikes may result in race conditions where an order arrives just as the spread collapses, leading to unexpected PO violation and rejection.

3. Flash crashes induce cascading rejections: over 88.9% of attempted Post-Only submissions fail during extreme volatility windows according to Hyperliquid’s March 2026 microstructure report.

4. Some exchanges do not support Post-Only for stop-market or trigger-based conditional orders, limiting its utility in risk-management workflows.

5. Order book depth mismatches between spot and perpetual markets create false confidence—PO validity in one instrument does not guarantee validity in another.

Verification Protocols for Active Orders

1. The order status must display “Open” with no “Filled” or “Partially Filled” indicators in the active orders tab.

2. The “Role” column in the order history must explicitly state “Maker”, never “Taker” or blank.

3. Executed trades linked to the order must show negative values in the fee field—e.g., −0.00012 BTC—not zero or positive.

4. The order ID must persist in the “Current Orders” list for at least three consecutive polling intervals without disappearing or transitioning to “Cancelled”.

5. Chain-level confirmation via on-chain transaction logs should reflect a single “OrderPlaced” event with no associated “OrderMatched” or “OrderCancelled” trace in the same block.

Frequently Asked Questions

Q: Can a Post-Only order be canceled after submission?A: Yes. Once accepted into the order book, it behaves identically to a standard limit order and supports full cancellation functionality via REST API or UI controls.

Q: Does Post-Only affect leverage or margin calculation?A: No. Margin requirements are determined solely by notional value, leverage setting, and underlying collateral—Post-Only status has zero impact on margin engine logic.

Q: Why do some exchanges reject Post-Only orders with “Price too close to market” errors?A: This occurs when the submitted price falls within a configurable tick tolerance—often set to one minimum price increment—designed to prevent edge-case spread crossings due to rounding artifacts.

Q: Is Post-Only available for all contract types on a given exchange?A: Not universally. Certain platforms disable Post-Only for inverse contracts, quanto swaps, or options series due to divergent settlement mechanics and price feed dependencies.