What Is an RPI (Retail Price Improvement) Order?

Overview

The Retail Price Improvement (RPI) order is a specialized order type designed to enhance liquidity quality and pricing efficiency for retail traders.
RPI orders interact exclusively with non-algorithmic participants, ensuring fair execution and a more transparent trading environment while maintaining overall market integrity.

Matching Rules

Exclusive Matching: RPI orders will only match with orders placed by non-algorithmic users. They do not execute against orders submitted via OpenAPI.
Post-Only Behavior: All RPI orders are strictly Post-Only, meaning they always act as maker orders and contribute liquidity to the order book.
Execution Priority: RPI orders have the lowest matching priority, regardless of when they are placed. They will only be filled after all non-RPI orders at the same price level have been executed.

How to Place an RPI Order

RPI orders can only be submitted via the OpenAPI.
- For API reference, please use the following parameter:
```
timeInForce = "RPIPostOnly"
```
Only approved market-making partners are authorized to place RPI orders.
Unauthorized users attempting to submit an RPI order will receive the following error message:

“RPI orders are restricted to approved Market Makers only.”

Trading Rules

Availability: RPI orders are currently supported on USDT-M and USDC-M Futures. Support for Inverse Futures and Spot trading will be added in upcoming updates.
Order Type: RPI orders function as Limit Orders, following the same margin requirements, order size limits, and price tick rules as standard limit orders.
Flexibility: RPI orders support batch placement, partial fills, order modification (price and quantity), and cancellation.
Incompatibility: RPI orders cannot be combined with conditional orders, such as Stop-Loss, Take-Profit, or Stop Orders.
Cross-Order Restriction: RPI orders cannot cross with non-RPI orders (i.e., when bid prices exceed ask prices).

Order Visibility

API Order Book: RPI orders are excluded from the API order book data.
Trading Page Order Book:
- RPI orders appear normally on the trading interface without any special label.
- However, crossed RPI orders (where bid > ask) are automatically hidden to maintain an organized order book.
- Hidden RPI orders remain active in the matching engine and can still execute when eligible.

Crossed Orders & Order Book Management

Crossed RPI orders occur when two RPI orders overlap in price (bid price > ask price).
In such cases:

Both orders will be hidden from the trading interface but remain active in the matching engine.
RPI orders will not match with each other, even when crossed.

Example:

Type	Price	Size	Whether visible in Order Book on the trading page
Bid3	203 (API Order)	10	Yes
Bid2	200 (RPI Order)	1	No
Bid1	199 (RPI Order)	150	No
Ask1	201 (RPI Order)	1	No
Ask2	200 (RPI Order)	200	No
Ask3	198 (API Order)	150	Yes

Frequently Asked Questions (FAQ)

1. Who can place RPI orders?
Only approved market-making partners can place RPI orders via the API. Unauthorized attempts will trigger an error message:

“RPI orders are restricted to approved Market Makers only.”

2. Will RPI orders appear in the order book?

API Order Book: ❌ Not visible
Trading Page Order Book: ✅ Visible (except crossed RPI orders, which remain hidden)

3. Do RPI orders execute immediately?
No. RPI orders are Post-Only maker orders, designed to add liquidity, not to take it.

4. How are RPI trades labeled?
RPI trades are labeled as “RPIPostOnly” in API order history for identification, but they do not carry any special tag on the trading interface.

Summary

RPI orders are an advanced liquidity feature that gives retail traders improved pricing opportunities while maintaining market balance.
By matching only with non-algorithmic flow and enforcing Post-Only execution, RPI orders ensure a fairer and more transparent trading experience on Phemex.

What is a RPI Order