> ## Documentation Index
> Fetch the complete documentation index at: https://api.corpay.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Functional Error Codes

## Overview

In addition to standard HTTP error responses, Fleet API may return **functional (business) errors** when a request is syntactically valid but cannot be processed due to business rules or system state.

These errors are returned as structured responses containing:

* An `errorCode`
* An `errorDescription`
* An appropriate HTTP `statusCode`

This document describes the **functional error codes** that clients may encounter and how to interpret them.

***

## Error Response Format

When a functional error occurs, the API returns a response in the following format:

```json theme={null}
{
  "errorCode": "ER-001",
  "errorDescription": "Invalid Card Number"
}
```

Clients should always inspect both:

* The HTTP status code
* The `errorCode` in the response body

***

## Functional Error Codes

### ER-001 — Invalid Card Number

**HTTP Status:** `400 Bad Request`

**Description**\
The supplied card number is not valid or does not exist in the Corpay system.

**Common causes:**

* Incorrect card number format
* Card number does not belong to the authenticated customer
* Card has been decommissioned

***

### ER-002 — Card Already Lodged

**HTTP Status:** `422 Unprocessable Entity`

**Description**\
The card has already been lodged and cannot be lodged again.

**Common causes:**

* Repeated lodging request for the same card
* Duplicate processing after a successful lodge operation

***

### ER-003 — Customer Associated With Card Is Not Active

**HTTP Status:** `400 Bad Request`

**Description**\
The customer account linked to the card is not in an active state.

**Common causes:**

* Customer is blocked or closed
* Card action attempted on an inactive account

***

### ER-004 — Card Is Not Active

**HTTP Status:** `400 Bad Request`

**Description**\
The requested operation cannot be performed because the card is not active.

**Common causes:**

* Card is blocked or cancelled
* Operation requires an active card state

***

### ER-005 — Invalid Request Parameters

**HTTP Status:** `400 Bad Request`

**Description**\
One or more request parameters failed validation.

**Notes:**\
The error message may include the invalid property name.

**Example:**

```text theme={null}
Invalid request parameters: vehicleRegNumber
```

***

### ER-006 — Invalid Request Parameter: customerAccountNumber

**HTTP Status:** `400 Bad Request`

**Description**\
The provided `customerAccountNumber` is invalid.

**Common causes:**

* Missing customer account number
* Invalid or unknown account number format

***

### ER-007 — Error Returned From Downstream Service

**HTTP Status:** `400 Bad Request`

**Description**\
A validation or processing error was returned by an internal or downstream service.

**Notes:**\
The returned `errorDescription` may vary depending on the underlying service failure.

***

### ER-009 — Invalid Hierarchy Level

**HTTP Status:** `400 Bad Request`

**Description**\
The requested operation violates the allowed customer hierarchy rules.

**Common causes:**

* Sub-customer creation beyond supported hierarchy depth
* Invalid parent - child relationship

***

### ER-010 — Invalid cardIdentifier

**HTTP Status:** `400 Bad Request`

**Description**\
The supplied `cardIdentifier` is invalid or does not exist.

**Common causes:**

* Incorrect identifier value
* Card does not belong to the authenticated customer
* Card has been removed from the system

***

### ER-011 — Card Not Replaced Successfully

**HTTP Status:** `400 Bad Request`

**Description**\
The card replacement process failed.

**Action required:**\
Please contact Corpay support or an administrator for further investigation.

***

### ER-012 — The server encountered an unexpected condition and could not complete the request. Please contact Corpay Support.

**HTTP Status:** `500 Internal Server Error`

**Description**\
The server encountered an unexpected condition and could not complete the request due to Technical error.

**Action required:**\
Please contact Corpay support or an administrator for further investigation.

***

## Handling Recommendations

When handling functional errors, clients should:

* Avoid retrying `400` and `422` responses automatically
* Display user-friendly error messages based on `errorCode`
* Correct input data before resubmitting requests
* Use query APIs as a fallback when webhook-driven flows fail
* Log `errorCode` and `errorDescription` for support diagnostics

***

## Summary

Functional error codes provide clear guidance when:

* Business rules are violated
* Resources are in an invalid state
* Operations cannot be completed safely

Always rely on the `errorCode` rather than just the HTTP status to determine next actions.