> ## Documentation Index
> Fetch the complete documentation index at: https://whitebit-mintlify-fix-broken-links-1774051868.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Order Parameter Rules

> Defines unsupported parameter combinations for order requests and explains related validation errors.

## Overview

The guide describes parameter combinations the API does not support and explains how to resolve related errors.

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## Retail Price Improvement (RPI) and IOC

RPI orders use post-only behavior by design. An RPI order does not support the IOC flag.

### Issue

A request sets both `rpi=true` and `ioc=true`.

### Result

The API rejects the request and returns error code `37`.

### Fix

Remove `ioc` when using `rpi`, or disable `rpi` when IOC behavior is required.