> ## 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.

# seat_added Event

> Track when additional seats are purchased.

Fires when additional seats are purchased. Use this event to measure expansion revenue from seat-based pricing.

## JavaScript

```javascript theme={null}
window._upstack('track', 'seat_added', {
  accountId: 'acct_abc123',
  subscriptionId: 'sub_def456',
  seatCount: 15,
  seatDelta: 5,
  mrrDelta: 2500
});
```

## Properties

| Property       | Type   | Required | Description                      |
| -------------- | ------ | -------- | -------------------------------- |
| accountId      | string | Yes      | Account identifier               |
| seatCount      | number | Yes      | Total seats after addition       |
| subscriptionId | string | No       | Subscription identifier          |
| seatDelta      | number | No       | Number of seats added            |
| mrrDelta       | number | No       | MRR increase from seats in cents |

## When to Fire

* When seats are purchased
* When user is added beyond plan limit
* When Stripe subscription quantity increases

## Stripe Webhook

Maps to `customer.subscription.updated` when subscription quantity increases.