curl --request POST \
  --url https://api.fastcac.com/v1/registrations/{registration_id}/documents \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form 'kind=<string>' \
  --form file=@example-file \
  --form proprietor=0

const form = new FormData();
form.append('kind', '<string>');
form.append('file', '<string>');
form.append('proprietor', '0');

const options = {method: 'POST', headers: {Authorization: 'Bearer <token>'}};

options.body = form;

fetch('https://api.fastcac.com/v1/registrations/{registration_id}/documents', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://api.fastcac.com/v1/registrations/{registration_id}/documents"

files = { "file": ("example-file", open("example-file", "rb")) }
payload = {
    "kind": "<string>",
    "proprietor": "0"
}
headers = {"Authorization": "Bearer <token>"}

response = requests.post(url, data=payload, files=files, headers=headers)

print(response.text)

package main

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

func main() {

	url := "https://api.fastcac.com/v1/registrations/{registration_id}/documents"

	payload := strings.NewReader("-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"kind\"\r\n\r\n<string>\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"file\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"proprietor\"\r\n\r\n0\r\n-----011000010111000001101001--")

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

	req.Header.Add("Authorization", "Bearer <token>")

	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/registrations/{registration_id}/documents",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => "-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"kind\"\r\n\r\n<string>\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"file\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"proprietor\"\r\n\r\n0\r\n-----011000010111000001101001--",
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: multipart/form-data"
  ],
]);

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

curl_close($curl);

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

{
  "object": "document",
  "id": "doc_3xj5qplEvHgc9iEaFUXBeV",
  "registration_id": "reg_6icg1TmXrQt1b78BtCmg6G",
  "proprietor": 0,
  "kind": "passport",
  "filename": "passport.jpg",
  "content_type": "image/jpeg",
  "size": 8,
  "status": "verified",
  "reason": null,
  "created_at": "2026-10-23T22:18:00Z"
}

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

{
  "error": {
    "type": "authentication_error",
    "code": "api_key_missing",
    "message": "Send your API key as `Authorization: Bearer <key>`.",
    "param": null,
    "request_id": "req_kdwpKsFMKS4VzLjqZJ0ntdrl"
  }
}

{
  "error": {
    "type": "permission_error",
    "code": "live_mode_unavailable",
    "message": "Live registrations aren't open yet. Use a test key (fc_test_…) for now.",
    "param": null,
    "request_id": "req_oYVCIHqeYbgIA3lIzwG0PO5r"
  }
}

{
  "error": {
    "type": "not_found_error",
    "code": "resource_missing",
    "message": "No such registration: reg_0000000000000000000000.",
    "param": "id",
    "request_id": "req_RlcFqswqrJZos4pnRMH3wa8d"
  }
}

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

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