curl --request POST \
  --url https://api.helloproper.com/one-time-bill-items \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "leaseId": "<string>",
  "oneTimeBillItem": {
    "productKey": "<string>",
    "description": "<string>",
    "amount": {
      "currency": "<string>",
      "amount": 123
    },
    "quantity": 123,
    "dueDate": "<string>",
    "accountingPeriod": "<string>",
    "vat": {
      "taxMode": "<string>",
      "taxRate": 123
    }
  }
}
'

import requests

url = "https://api.helloproper.com/one-time-bill-items"

payload = {
    "leaseId": "<string>",
    "oneTimeBillItem": {
        "productKey": "<string>",
        "description": "<string>",
        "amount": {
            "currency": "<string>",
            "amount": 123
        },
        "quantity": 123,
        "dueDate": "<string>",
        "accountingPeriod": "<string>",
        "vat": {
            "taxMode": "<string>",
            "taxRate": 123
        }
    }
}
headers = {
    "Authorization": "<api-key>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: '<api-key>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    leaseId: '<string>',
    oneTimeBillItem: {
      productKey: '<string>',
      description: '<string>',
      amount: {currency: '<string>', amount: 123},
      quantity: 123,
      dueDate: '<string>',
      accountingPeriod: '<string>',
      vat: {taxMode: '<string>', taxRate: 123}
    }
  })
};

fetch('https://api.helloproper.com/one-time-bill-items', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.helloproper.com/one-time-bill-items",
  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([
    'leaseId' => '<string>',
    'oneTimeBillItem' => [
        'productKey' => '<string>',
        'description' => '<string>',
        'amount' => [
                'currency' => '<string>',
                'amount' => 123
        ],
        'quantity' => 123,
        'dueDate' => '<string>',
        'accountingPeriod' => '<string>',
        'vat' => [
                'taxMode' => '<string>',
                'taxRate' => 123
        ]
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: <api-key>",
    "Content-Type: application/json"
  ],
]);

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

curl_close($curl);

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

package main

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

func main() {

	url := "https://api.helloproper.com/one-time-bill-items"

	payload := strings.NewReader("{\n  \"leaseId\": \"<string>\",\n  \"oneTimeBillItem\": {\n    \"productKey\": \"<string>\",\n    \"description\": \"<string>\",\n    \"amount\": {\n      \"currency\": \"<string>\",\n      \"amount\": 123\n    },\n    \"quantity\": 123,\n    \"dueDate\": \"<string>\",\n    \"accountingPeriod\": \"<string>\",\n    \"vat\": {\n      \"taxMode\": \"<string>\",\n      \"taxRate\": 123\n    }\n  }\n}")

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

	req.Header.Add("Authorization", "<api-key>")
	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))

}

HttpResponse<String> response = Unirest.post("https://api.helloproper.com/one-time-bill-items")
  .header("Authorization", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"leaseId\": \"<string>\",\n  \"oneTimeBillItem\": {\n    \"productKey\": \"<string>\",\n    \"description\": \"<string>\",\n    \"amount\": {\n      \"currency\": \"<string>\",\n      \"amount\": 123\n    },\n    \"quantity\": 123,\n    \"dueDate\": \"<string>\",\n    \"accountingPeriod\": \"<string>\",\n    \"vat\": {\n      \"taxMode\": \"<string>\",\n      \"taxRate\": 123\n    }\n  }\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.helloproper.com/one-time-bill-items")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = '<api-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"leaseId\": \"<string>\",\n  \"oneTimeBillItem\": {\n    \"productKey\": \"<string>\",\n    \"description\": \"<string>\",\n    \"amount\": {\n      \"currency\": \"<string>\",\n      \"amount\": 123\n    },\n    \"quantity\": 123,\n    \"dueDate\": \"<string>\",\n    \"accountingPeriod\": \"<string>\",\n    \"vat\": {\n      \"taxMode\": \"<string>\",\n      \"taxRate\": 123\n    }\n  }\n}"

response = http.request(request)
puts response.read_body

{
  "oneTimeBillItemId": "<string>",
  "dueDate": "<string>"
}