Add Subscription Add-on

POST

subscriptions

{id}

addons

Attach an add-on plan to a subscription

curl --request POST \
  --url https://billing.example.com/v1/subscriptions/{id}/addons \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "plan_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "quantity": 2
}
'

import requests

url = "https://billing.example.com/v1/subscriptions/{id}/addons"

payload = {
    "plan_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "quantity": 2
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({plan_id: '3c90c3cc-0d44-4b50-8888-8dd25736052a', quantity: 2})
};

fetch('https://billing.example.com/v1/subscriptions/{id}/addons', 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://billing.example.com/v1/subscriptions/{id}/addons",
  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([
    'plan_id' => '3c90c3cc-0d44-4b50-8888-8dd25736052a',
    'quantity' => 2
  ]),
  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;
}

package main

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

func main() {

	url := "https://billing.example.com/v1/subscriptions/{id}/addons"

	payload := strings.NewReader("{\n  \"plan_id\": \"3c90c3cc-0d44-4b50-8888-8dd25736052a\",\n  \"quantity\": 2\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))

}

HttpResponse<String> response = Unirest.post("https://billing.example.com/v1/subscriptions/{id}/addons")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"plan_id\": \"3c90c3cc-0d44-4b50-8888-8dd25736052a\",\n  \"quantity\": 2\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://billing.example.com/v1/subscriptions/{id}/addons")

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

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"plan_id\": \"3c90c3cc-0d44-4b50-8888-8dd25736052a\",\n  \"quantity\": 2\n}"

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

{
  "data": {
    "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "tenant_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "subscription_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "plan_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "quantity": 123,
    "created_at": "2023-11-07T05:31:56Z"
  }
}

{
  "error": {
    "code": "validation_failed",
    "message": "<string>"
  }
}

{
  "error": {
    "code": "validation_failed",
    "message": "<string>"
  }
}

{
  "error": {
    "code": "validation_failed",
    "message": "<string>"
  }
}

Attaches an existing plan to a subscription as an add-on. The subscription’s base plan is unchanged; the add-on is billed as an extra line — add-on plan price × quantity, taxed independently — starting from the next recurring invoice. Nothing is charged now and no mid-cycle proration is applied in v1. The add-on plan’s currency must match the subscription’s base-plan currency. List what is attached with List Subscription Add-ons and detach with Remove Subscription Add-on.

Path Parameters

Parameter	Type	Required	Description
`id`	string (uuid)	Yes	The subscription ID.

Request Body

Parameter	Type	Required	Description
`plan_id`	string (uuid)	Yes	The plan to attach as an add-on. Must have a price in the subscription’s currency.
`quantity`	integer	Yes	Units billed each period. Minimum `1`.

Example Request

curl -X POST https://api.recurso.dev/v1/subscriptions/b9071c55-0e14-4720-80f3-665613ceb7de/addons \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "plan_id": "4e5f6a7b-8c9d-4e0f-a1b2-c3d4e5f6a7b8",
    "quantity": 3
  }'

Response

Returns 201 Created with the new add-on.

{
  "data": {
    "id": "d3a7f1c2-5b8e-4c90-a6d1-2e3f4a5b6c7d",
    "tenant_id": "0f9e8d7c-6b5a-4f3e-9d2c-1b0a9f8e7d6c",
    "subscription_id": "b9071c55-0e14-4720-80f3-665613ceb7de",
    "plan_id": "4e5f6a7b-8c9d-4e0f-a1b2-c3d4e5f6a7b8",
    "quantity": 3,
    "created_at": "2026-08-20T09:15:00Z"
  }
}

Fields

Field	Type	Description
`id`	string (uuid)	The add-on ID — pass it as `addonId` to remove the add-on
`tenant_id`	string (uuid)	Owning tenant
`subscription_id`	string (uuid)	The subscription the add-on is attached to
`plan_id`	string (uuid)	The plan billed as an add-on
`quantity`	integer	Number of add-on units billed each period
`created_at`	string (date-time)	When the add-on was attached

The first invoice carrying the add-on line is the next renewal. To bill an add-on for the remainder of the current period, change the plan instead — preview the proration with Preview Plan Change.

Errors

Status	Code	When	Fix
400	`validation_failed`	`id` is not a valid UUID, the body fails binding (`plan_id` missing or not a UUID, `quantity` missing or below `1`), or the add-on plan’s currency does not match the subscription’s currency.	Send a valid UUID and a `quantity` of at least `1`; pick a plan priced in the subscription’s currency.
401	`unauthorized`	API key missing or invalid (`invalid_api_key`), or a live/test mode mismatch (`key_mode_mismatch`).	Send `Authorization: Bearer <api_key>` with a key for the right mode.
404	`not_found`	The subscription does not exist in your tenant, or `plan_id` does not resolve to a plan with at least one price.	Verify the subscription with `GET /v1/subscriptions/{id}` and the plan with `GET /v1/plans/{id}`.

Errors use the standard envelope — see Errors.

Authorizations

Authorization

string

header

required

Tenant API key obtained from POST /auth/register or POST /v1/developer/keys.

Path Parameters

string<uuid>

required

Body

application/json

plan_id

string<uuid>

required

The plan to attach as an add-on.

quantity

integer

required

Required range: x >= 1

Response

Add-on attached.

data

object

An existing plan attached to a subscription with a quantity (Multi-product catalog v1). Billed as an extra line — add-on plan price × quantity, taxed independently — from the subscription's next recurring invoice.

Show child attributes

Attach an add-on plan to a subscription

curl --request POST \
  --url https://billing.example.com/v1/subscriptions/{id}/addons \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "plan_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "quantity": 2
}
'

import requests

url = "https://billing.example.com/v1/subscriptions/{id}/addons"

payload = {
    "plan_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "quantity": 2
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({plan_id: '3c90c3cc-0d44-4b50-8888-8dd25736052a', quantity: 2})
};

fetch('https://billing.example.com/v1/subscriptions/{id}/addons', 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://billing.example.com/v1/subscriptions/{id}/addons",
  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([
    'plan_id' => '3c90c3cc-0d44-4b50-8888-8dd25736052a',
    'quantity' => 2
  ]),
  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;
}

package main

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

func main() {

	url := "https://billing.example.com/v1/subscriptions/{id}/addons"

	payload := strings.NewReader("{\n  \"plan_id\": \"3c90c3cc-0d44-4b50-8888-8dd25736052a\",\n  \"quantity\": 2\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))

}

HttpResponse<String> response = Unirest.post("https://billing.example.com/v1/subscriptions/{id}/addons")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"plan_id\": \"3c90c3cc-0d44-4b50-8888-8dd25736052a\",\n  \"quantity\": 2\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://billing.example.com/v1/subscriptions/{id}/addons")

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

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"plan_id\": \"3c90c3cc-0d44-4b50-8888-8dd25736052a\",\n  \"quantity\": 2\n}"

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

{
  "data": {
    "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "tenant_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "subscription_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "plan_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "quantity": 123,
    "created_at": "2023-11-07T05:31:56Z"
  }
}

{
  "error": {
    "code": "validation_failed",
    "message": "<string>"
  }
}

{
  "error": {
    "code": "validation_failed",
    "message": "<string>"
  }
}

{
  "error": {
    "code": "validation_failed",
    "message": "<string>"
  }
}

Getting Started

Core

Billing & Invoicing

Revenue & Finance

Growth & Recovery

Compliance (India)

Platform

Customer Portal API

Add Subscription Add-on

Path Parameters

Request Body

Example Request

Response

Fields

Errors

Authorizations

Path Parameters

Body

Response

​Path Parameters

​Request Body

​Example Request

​Response

​Fields

​Errors

Authorizations

Path Parameters

Body

Response

Path Parameters

Request Body

Example Request

Response

Fields

Errors