curl --request POST \
  --url https://api.stigg.io/api/v1/contracts/{id}/subscriptions \
  --header 'Content-Type: application/json' \
  --header 'X-API-KEY: <api-key>' \
  --data '
{
  "subscriptions": [
    {
      "existingSubscriptionId": "<string>"
    }
  ],
  "subscriptionIds": [
    "<string>"
  ]
}
'

import requests

url = "https://api.stigg.io/api/v1/contracts/{id}/subscriptions"

payload = {
    "subscriptions": [{ "existingSubscriptionId": "<string>" }],
    "subscriptionIds": ["<string>"]
}
headers = {
    "X-API-KEY": "<api-key>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {'X-API-KEY': '<api-key>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    subscriptions: [{existingSubscriptionId: '<string>'}],
    subscriptionIds: ['<string>']
  })
};

fetch('https://api.stigg.io/api/v1/contracts/{id}/subscriptions', 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.stigg.io/api/v1/contracts/{id}/subscriptions",
  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([
    'subscriptions' => [
        [
                'existingSubscriptionId' => '<string>'
        ]
    ],
    'subscriptionIds' => [
        '<string>'
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "X-API-KEY: <api-key>"
  ],
]);

$response = curl_exec($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.stigg.io/api/v1/contracts/{id}/subscriptions"

	payload := strings.NewReader("{\n  \"subscriptions\": [\n    {\n      \"existingSubscriptionId\": \"<string>\"\n    }\n  ],\n  \"subscriptionIds\": [\n    \"<string>\"\n  ]\n}")

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

	req.Header.Add("X-API-KEY", "<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.stigg.io/api/v1/contracts/{id}/subscriptions")
  .header("X-API-KEY", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"subscriptions\": [\n    {\n      \"existingSubscriptionId\": \"<string>\"\n    }\n  ],\n  \"subscriptionIds\": [\n    \"<string>\"\n  ]\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.stigg.io/api/v1/contracts/{id}/subscriptions")

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

request = Net::HTTP::Post.new(url)
request["X-API-KEY"] = '<api-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"subscriptions\": [\n    {\n      \"existingSubscriptionId\": \"<string>\"\n    }\n  ],\n  \"subscriptionIds\": [\n    \"<string>\"\n  ]\n}"

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

{
  "data": {
    "contractId": "contract-acme-2026",
    "billingId": "ct_1a2b3c4d",
    "id": "3452155b-deca-4d7f-91e5-82d486dc8bb0",
    "refId": "contract-acme-2026",
    "poNumber": "PO-4821",
    "externalId": "contract-acme-2026",
    "customerExternalId": "customer-acme",
    "name": "PO-4821",
    "state": "ACTIVE",
    "billingState": "ACTIVE",
    "activationStartDate": "2026-01-01T00:00:00.000Z",
    "activationEndDate": "2026-12-31T00:00:00.000Z",
    "createdAt": "2025-12-15T09:30:00.000Z",
    "nextInvoice": {
      "invoiceId": "a3f1c2de-5b47-4c8e-9f10-2d6b8e4a7c31",
      "amount": {
        "amount": 4900,
        "currency": "usd"
      },
      "dueDate": "2026-08-01T00:00:00.000Z",
      "periodStart": "2026-07-01T00:00:00.000Z",
      "periodEnd": "2026-08-01T00:00:00.000Z"
    },
    "latestInvoice": {
      "billingId": "inv_abc123",
      "status": "OPEN",
      "createdAt": "2026-07-01T00:00:00.000Z",
      "total": 4900,
      "amountDue": 4900,
      "currency": "usd",
      "pdfUrl": null,
      "requiresAction": false,
      "billingReason": null
    },
    "subscriptions": [
      {
        "subscriptionId": "subscription-acme-platform",
        "planDisplayName": "Enterprise Platform",
        "productDisplayName": "Revvenu"
      }
    ]
  }
}

{
  "message": "<string>",
  "code": "BadUserInput",
  "reason": "<string>"
}

{
  "message": "<string>",
  "code": "Unauthenticated"
}

{
  "message": "<string>",
  "code": "IdentityForbidden"
}

{
  "message": "<string>",
  "code": "CustomerNotFound"
}

{
  "message": "<string>",
  "code": "DuplicatedEntityNotAllowed"
}

{
  "message": "<string>",
  "code": "RateLimitExceeded"
}