curl --request POST \
  --url https://api.fastcac.com/v1/businesses/monitors \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "number": "RC 7654321",
  "external_id": "merchant-4471"
}
'

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({number: 'RC 7654321', external_id: 'merchant-4471'})
};

fetch('https://api.fastcac.com/v1/businesses/monitors', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://api.fastcac.com/v1/businesses/monitors"

payload = {
    "number": "RC 7654321",
    "external_id": "merchant-4471"
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.fastcac.com/v1/businesses/monitors"

	payload := strings.NewReader("{\n  \"number\": \"RC 7654321\",\n  \"external_id\": \"merchant-4471\"\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.fastcac.com/v1/businesses/monitors",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'number' => 'RC 7654321',
    'external_id' => 'merchant-4471'
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

{
  "object": "business_monitor",
  "id": "mon_5Rfxqm9UQ4xlFxXoJeFCaT",
  "number": "7654321",
  "type": "RC",
  "type_label": "Company",
  "name": "ADA FOODS LIMITED",
  "status": "ACTIVE",
  "active": true,
  "external_id": "merchant-4471",
  "state": "active",
  "paid_through": "2026-11-27T15:16:04Z",
  "last_checked_at": null,
  "last_changed_at": null,
  "amount_charged": "100.00",
  "created_at": "2026-10-28T15:16:04Z"
}

{
  "error": {
    "type": "invalid_request_error",
    "code": "<string>",
    "message": "<string>",
    "param": "<string>",
    "request_id": "<string>",
    "details": {}
  }
}

{
  "error": {
    "type": "authentication_error",
    "code": "api_key_missing",
    "message": "Send your API key as `Authorization: Bearer <key>`.",
    "param": null,
    "request_id": "req_8r9FEwNmLuxQORZX5Qhvkd0q"
  }
}

{
  "error": {
    "type": "payment_error",
    "code": "insufficient_balance",
    "message": "Your balance is ₦0.00; monitoring a business costs ₦100.00 for 30 days. Fund your wallet by bank transfer to your funding account, then try again.",
    "param": null,
    "request_id": "req_GV3JxZlBlquNBBSjEqFGHnag",
    "details": {
      "amount_due": "100.00",
      "balance": "0.00",
      "currency": "NGN",
      "funding_account": {
        "account_number": "0000000000",
        "bank_name": "TEST BANK",
        "account_name": "FastCAC - TEST MODE"
      }
    }
  }
}

{
  "error": {
    "type": "permission_error",
    "code": "live_mode_unavailable",
    "message": "Live registrations are paused right now. Use a test key (fc_test_…) meanwhile.",
    "param": null,
    "request_id": "req_Td9lI1vsT5ARzv0XD7RGS1tD"
  }
}

{
  "error": {
    "type": "not_found_error",
    "code": "cac_record_missing",
    "message": "CAC has no business with that number. You weren't charged.",
    "param": "number",
    "request_id": "req_Y68cfGTTJjBHCCRQaS2tDHhh"
  }
}

{
  "error": {
    "type": "invalid_request_error",
    "code": "monitor_exists",
    "message": "You already monitor RC 7654321.",
    "param": "number",
    "request_id": "req_pih9euyk6J6Ge0u2TkjaNeO8",
    "details": {
      "monitor": "mon_5Rfxqm9UQ4xlFxXoJeFCaT"
    }
  }
}

{
  "error": {
    "type": "invalid_request_error",
    "code": "<string>",
    "message": "<string>",
    "param": "<string>",
    "request_id": "<string>",
    "details": {}
  }
}