> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.trygrant.com/api-reference/grant-events-api/subscriptions/change-plan/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.trygrant.com/_mcp/server.

# Change subscription plan

POST https://api.trygrant.com/v1/subscriptions/{id}/change-plan
Content-Type: application/json

Changes a subscription to a new plan immediately or schedules the change for end of period.

Reference: https://docs.trygrant.com/api-reference/grant-events-api/subscriptions/change-plan

## Authentication

- `Authorization` header (bearer token, required) — API key obtained from the Grant dashboard

## Servers

- `https://api.trygrant.com` (Production, default)
- `http://localhost:8787` (Local development)

## Request

### Path parameters

- `id` (string, required)

### Body (application/json)

This endpoint expects a ChangePlanRequest.

- `target_plan_code` (string, required) — Target plan code to transition this subscription to
- `change_mode` (enum, required) — When to change plan: "now" transitions immediately, "end_of_period" transitions at the end of the current billing cycle
  - Allowed values: `now`, `end_of_period`
- `cancel_now_prepaid_refund_policy` (enum, optional) — Applies only when change_mode is "now": refund prorated prepaid fixed fees or skip refunds.
  - Allowed values: `refund_prorated_prepaid_fixed_fees`, `no_refund_prepaid_fixed_fees`

## Response

### 200

Plan change completed or scheduled

- `success` (boolean, required)
- `status` (enum, required) — Whether plan transition is complete now or scheduled
  - Allowed values: `completed`, `scheduled`
- `old_subscription` (Subscription, required)
- `new_subscription` (ChangePlanResponseNewSubscription, required, nullable)
- `request_id` (string, required)

## Errors

### 400 Bad Request Error

Invalid request

- `success` (boolean, required)
- `error` (ErrorResponseError, required)
- `request_id` (string, optional) — Request ID for tracing

### 401 Unauthorized Error

Unauthorized

- `success` (boolean, required)
- `error` (ErrorResponseError, required)
- `request_id` (string, optional) — Request ID for tracing

### 404 Not Found Error

Subscription not found

- `success` (boolean, required)
- `error` (ErrorResponseError, required)
- `request_id` (string, optional) — Request ID for tracing

### 409 Conflict Error

Conflict

- `success` (boolean, required)
- `error` (ErrorResponseError, required)
- `request_id` (string, optional) — Request ID for tracing

### 500 Internal Server Error

Internal server error

- `success` (boolean, required)
- `error` (ErrorResponseError, required)
- `request_id` (string, optional) — Request ID for tracing

## Types

### Subscription

- `id` (string, required)
- `customer_id` (string, required)
- `plan_id` (string, required)
- `plan_code` (string, required, nullable) — Human-readable plan code
- `status` (enum, required)
  - Allowed values: `pending_payment_method`, `trialing`, `active`, `past_due`, `canceled`
- `start_date` (string, required) — ISO 8601 subscription start date
- `billing_anchor_day` (integer, required) — Day of month for billing anchor
- `next_renewal_date` (string, required, nullable) — ISO 8601 next renewal date
- `cancel_at_period_end` (boolean, required) — True when cancellation is scheduled for the end of the current billable period
- `cancel_at` (string, required, nullable) — ISO 8601 scheduled cancellation timestamp
- `plan_transition_at_period_end` (boolean, required) — True when a plan transition is scheduled for end of current billable period
- `plan_transition_at` (string, required, nullable) — ISO 8601 scheduled plan transition timestamp
- `plan_transition_to_plan_id` (string, required, nullable) — Target plan ID for a scheduled transition
- `canceled_at` (string, required, nullable) — ISO 8601 actual cancellation timestamp (set when status transitions to canceled)
- `created_at` (string, required) — ISO 8601 creation timestamp
- `updated_at` (string, required) — ISO 8601 last-updated timestamp

### ChangePlanResponseNewSubscription

- `id` (string, required)
- `customer_id` (string, required)
- `plan_id` (string, required)
- `plan_code` (string, required, nullable) — Human-readable plan code
- `status` (enum, required)
  - Allowed values: `pending_payment_method`, `trialing`, `active`, `past_due`, `canceled`
- `start_date` (string, required) — ISO 8601 subscription start date
- `billing_anchor_day` (integer, required) — Day of month for billing anchor
- `next_renewal_date` (string, required, nullable) — ISO 8601 next renewal date
- `cancel_at_period_end` (boolean, required) — True when cancellation is scheduled for the end of the current billable period
- `cancel_at` (string, required, nullable) — ISO 8601 scheduled cancellation timestamp
- `plan_transition_at_period_end` (boolean, required) — True when a plan transition is scheduled for end of current billable period
- `plan_transition_at` (string, required, nullable) — ISO 8601 scheduled plan transition timestamp
- `plan_transition_to_plan_id` (string, required, nullable) — Target plan ID for a scheduled transition
- `canceled_at` (string, required, nullable) — ISO 8601 actual cancellation timestamp (set when status transitions to canceled)
- `created_at` (string, required) — ISO 8601 creation timestamp
- `updated_at` (string, required) — ISO 8601 last-updated timestamp

### ErrorResponseError

- `code` (string, required)
- `message` (string, required)
- `details` (any, optional)

## Examples

**Request**

```json
{
  "target_plan_code": "starter_monthly",
  "change_mode": "now"
}
```

**Response**

```json
{
  "success": true,
  "status": "completed",
  "old_subscription": {
    "id": "cm5x9z8nv0000h85r7l9p2k1m",
    "customer_id": "cm5x9z8nv0001h85r7l9p2k2m",
    "plan_id": "cm5x9z8nv0002h85r7l9p2k3m",
    "plan_code": "starter_plan",
    "status": "active",
    "start_date": "2024-01-15T00:00:00.000Z",
    "billing_anchor_day": 1,
    "next_renewal_date": "2024-02-15T00:00:00.000Z",
    "cancel_at_period_end": false,
    "cancel_at": null,
    "plan_transition_at_period_end": false,
    "plan_transition_at": null,
    "plan_transition_to_plan_id": null,
    "canceled_at": null,
    "created_at": "2024-01-15T10:30:00.000Z",
    "updated_at": "2024-01-15T10:30:00.000Z"
  },
  "new_subscription": {
    "id": "cm5x9z8nv0000h85r7l9p2k1m",
    "customer_id": "cm5x9z8nv0001h85r7l9p2k2m",
    "plan_id": "cm5x9z8nv0002h85r7l9p2k3m",
    "plan_code": "starter_plan",
    "status": "active",
    "start_date": "2024-01-15T00:00:00.000Z",
    "billing_anchor_day": 1,
    "next_renewal_date": "2024-02-15T00:00:00.000Z",
    "cancel_at_period_end": false,
    "cancel_at": null,
    "plan_transition_at_period_end": false,
    "plan_transition_at": null,
    "plan_transition_to_plan_id": null,
    "canceled_at": null,
    "created_at": "2024-01-15T10:30:00.000Z",
    "updated_at": "2024-01-15T10:30:00.000Z"
  },
  "request_id": "req_abc123"
}
```

**SDK Code**

```python
import requests

url = "https://api.trygrant.com/v1/subscriptions/cm5x9z8nv0000h85r7l9p2k1m/change-plan"

payload = {
    "target_plan_code": "starter_monthly",
    "change_mode": "now"
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

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

print(response.json())
```

```javascript
const url = 'https://api.trygrant.com/v1/subscriptions/cm5x9z8nv0000h85r7l9p2k1m/change-plan';
const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: '{"target_plan_code":"starter_monthly","change_mode":"now"}'
};

try {
  const response = await fetch(url, options);
  const data = await response.json();
  console.log(data);
} catch (error) {
  console.error(error);
}
```

```go
package main

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

func main() {

	url := "https://api.trygrant.com/v1/subscriptions/cm5x9z8nv0000h85r7l9p2k1m/change-plan"

	payload := strings.NewReader("{\n  \"target_plan_code\": \"starter_monthly\",\n  \"change_mode\": \"now\"\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(res)
	fmt.Println(string(body))

}
```

```ruby
require 'uri'
require 'net/http'

url = URI("https://api.trygrant.com/v1/subscriptions/cm5x9z8nv0000h85r7l9p2k1m/change-plan")

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  \"target_plan_code\": \"starter_monthly\",\n  \"change_mode\": \"now\"\n}"

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

```java
import com.mashape.unirest.http.HttpResponse;
import com.mashape.unirest.http.Unirest;

HttpResponse<String> response = Unirest.post("https://api.trygrant.com/v1/subscriptions/cm5x9z8nv0000h85r7l9p2k1m/change-plan")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"target_plan_code\": \"starter_monthly\",\n  \"change_mode\": \"now\"\n}")
  .asString();
```

```php
<?php
require_once('vendor/autoload.php');

$client = new \GuzzleHttp\Client();

$response = $client->request('POST', 'https://api.trygrant.com/v1/subscriptions/cm5x9z8nv0000h85r7l9p2k1m/change-plan', [
  'body' => '{
  "target_plan_code": "starter_monthly",
  "change_mode": "now"
}',
  'headers' => [
    'Authorization' => 'Bearer <token>',
    'Content-Type' => 'application/json',
  ],
]);

echo $response->getBody();
```

```csharp
using RestSharp;

var client = new RestClient("https://api.trygrant.com/v1/subscriptions/cm5x9z8nv0000h85r7l9p2k1m/change-plan");
var request = new RestRequest(Method.POST);
request.AddHeader("Authorization", "Bearer <token>");
request.AddHeader("Content-Type", "application/json");
request.AddParameter("application/json", "{\n  \"target_plan_code\": \"starter_monthly\",\n  \"change_mode\": \"now\"\n}", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
```

```swift
import Foundation

let headers = [
  "Authorization": "Bearer <token>",
  "Content-Type": "application/json"
]
let parameters = [
  "target_plan_code": "starter_monthly",
  "change_mode": "now"
] as [String : Any]

let postData = JSONSerialization.data(withJSONObject: parameters, options: [])

let request = NSMutableURLRequest(url: NSURL(string: "https://api.trygrant.com/v1/subscriptions/cm5x9z8nv0000h85r7l9p2k1m/change-plan")! as URL,
                                        cachePolicy: .useProtocolCachePolicy,
                                    timeoutInterval: 10.0)
request.httpMethod = "POST"
request.allHTTPHeaderFields = headers
request.httpBody = postData as Data

let session = URLSession.shared
let dataTask = session.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
  if (error != nil) {
    print(error as Any)
  } else {
    let httpResponse = response as? HTTPURLResponse
    print(httpResponse)
  }
})

dataTask.resume()
```

> API documentation for Grant — billing infrastructure for usage-based pricing