---
title: SetMonthlyContactExternalID (REST)
description: "Allows for manually created contacts to be converted and controlled by the Monthly APIs. This allows customers to associate external IDs with existing Flash Contacts. ## POST ### POST [/api/monthly/SetMonthlyContactExternalID](https://int1aa.azurewebsites.net/swagger/ui/index#!/Monthly/Monthly_SetMonthlyContactExternalID) ``` securityToken: \"string\" ``` ``` { \"ContactGuid\": \"string\", \"ContactId\": \"string\", \"FlashAccountNumber\":…"
url: "https://qa.flashparking.com/docs/setmonthlycontactexternalid-rest/"
updated: "2025-12-19"
category: "3rd Party API Integrations / Monthly APIs / Monthly API Calls & Guide - REST"
---

# SetMonthlyContactExternalID (REST)

Allows for manually created contacts to be converted and controlled by the Monthly APIs. This allows customers to associate external IDs with existing Flash Contacts.

## POST

### POST [/api/monthly/SetMonthlyContactExternalID](https://int1aa.azurewebsites.net/swagger/ui/index#!/Monthly/Monthly_SetMonthlyContactExternalID)

```
securityToken: "string"
```

```
{
  "ContactGuid": "string",
  "ContactId": "string",
  "FlashAccountNumber": "string",
  "LocationId": "string"
}
```

### Parameters

| **Value** | **Required Field** | **Description** | **Data Type** |
| --- | --- | --- | --- |
| `securityToken` | Yes | We provide you with a security token in GUID format. Note that this security token will differ from location to location. Your security token for the Monthly API is *not *used globally across all locations. We will provide you with a different security token per each location you create monthly accounts for. | `string `(GUID format) |
| `ContactGuid` | Yes | Flash generated unique value in GUID format. | `string `(GUID format) |
| `ContactId` | Yes | Third Party system generated unique value or the Flash Internal account number. This is the value that is desired to set the External Contact ID to. The Third Party contact ID number is external and different from the internal contact ID generated by the Flash system. | `string` |
| **`FlashAccountNumber`** | Yes | Flash system generated account number. | `string` |
| **`LocationId`** | Yes | We provide you with a location ID in GUID format. The location ID corresponds with the location you are creating monthly accounts for. | `string` (GUID format) |

## Response

### Example

```
{
  "Code": "Success",
  "Message": "string",
  "LocationProfiles": [
    {
      "UniqueID": "00000000-0000-0000-0000-000000000000",
      "Name": "string"
    }
  ]
}
```

### Parameters

The response should include **S`etMonthlyContactExternalID`**object with the following data:

| **Field** | **Description** |
| --- | --- |
| `Code` | If the request succeeded, the value of **RESULT_CODE **will be **Success**. If the request failed, a relevant error code will be provided. |
| `Message` | A message with clarifying information about the result is provided in this field. |