> ## Documentation Index
> Fetch the complete documentation index at: https://docs.upstackdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# subscription_started Event

> Track when a new subscription begins (first billing period starts).

Fires when a new subscription begins (first billing period starts). This marks the start of paid service.

## JavaScript

```javascript theme={null}
window._upstack('track', 'subscription_started', {
  subscriptionId: 'sub_def456',
  accountId: 'acct_abc123',
  planId: 'plan_pro_monthly',
  planName: 'Pro Plan',
  mrr: 9900,
  billingInterval: 'month'
});
```

## Properties

| Property        | Type   | Required | Description                        |
| --------------- | ------ | -------- | ---------------------------------- |
| subscriptionId  | string | Yes      | Subscription identifier            |
| accountId       | string | Yes      | Account identifier                 |
| planId          | string | Yes      | Plan identifier                    |
| planName        | string | No       | Plan display name                  |
| mrr             | number | No       | Monthly recurring revenue in cents |
| billingInterval | string | No       | Billing frequency                  |

## When to Fire

* After first successful charge
* When subscription status becomes `active`
* After trial converts to paid