curl --request POST \
  --url https://api.tilta.io/v1/invoices/{external_id}/files \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form 'files={
  "type": "file",
  "fieldname": "<string>",
  "filename": "<string>",
  "encoding": "<string>",
  "mimetype": "<string>"
}' \
  --form 'types={
  "type": "field",
  "fieldname": "<string>",
  "mimetype": "<string>",
  "encoding": "<string>",
  "fieldnameTruncated": true,
  "valueTruncated": true
}'

const form = new FormData();
form.append('files', '{
  "type": "file",
  "fieldname": "<string>",
  "filename": "<string>",
  "encoding": "<string>",
  "mimetype": "<string>"
}');
form.append('types', '{
  "type": "field",
  "fieldname": "<string>",
  "mimetype": "<string>",
  "encoding": "<string>",
  "fieldnameTruncated": true,
  "valueTruncated": true
}');

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

options.body = form;

fetch('https://api.tilta.io/v1/invoices/{external_id}/files', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://api.tilta.io/v1/invoices/{external_id}/files"

payload = "-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"files\"\r\n\r\n{\r\n  \"type\": \"file\",\r\n  \"fieldname\": \"<string>\",\r\n  \"filename\": \"<string>\",\r\n  \"encoding\": \"<string>\",\r\n  \"mimetype\": \"<string>\"\r\n}\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"types\"\r\n\r\n{\r\n  \"type\": \"field\",\r\n  \"fieldname\": \"<string>\",\r\n  \"mimetype\": \"<string>\",\r\n  \"encoding\": \"<string>\",\r\n  \"fieldnameTruncated\": true,\r\n  \"valueTruncated\": true\r\n}\r\n-----011000010111000001101001--"
headers = {"Authorization": "Bearer <token>"}

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

print(response.text)

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.tilta.io/v1/invoices/{external_id}/files",
  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=\"files\"\r\n\r\n{\r\n  \"type\": \"file\",\r\n  \"fieldname\": \"<string>\",\r\n  \"filename\": \"<string>\",\r\n  \"encoding\": \"<string>\",\r\n  \"mimetype\": \"<string>\"\r\n}\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"types\"\r\n\r\n{\r\n  \"type\": \"field\",\r\n  \"fieldname\": \"<string>\",\r\n  \"mimetype\": \"<string>\",\r\n  \"encoding\": \"<string>\",\r\n  \"fieldnameTruncated\": true,\r\n  \"valueTruncated\": true\r\n}\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;
}

"<string>"

{
  "code": "BAD_REQUEST",
  "error": "Request validation failed. 1 issue found.",
  "issues": [
    {
      "code": "INVALID_TYPE",
      "path": "body.registered_at",
      "message": "Invalid type"
    }
  ]
}

{
  "error": "Unauthorized",
  "code": "UNAUTHORIZED"
}