Payload

All webhook payloads follow a consistent top-level structure with event-specific data nested within the data object.

subscriptionIdstring

The subscription the payment method was saved for.

customerIdstring

The customer ID. Returns your externalId if you provided one when creating the customer, otherwise returns the Commet publicId.

cardobject | null

Card display metadata: brand, last4, expMonth, expYear. Null when the method is not a card or its details cannot be retrieved.

{
  "event": "payment_method.attached",
  "timestamp": "2026-03-25T14:32:00.000Z",
  "organizationId": "org_abc123",
  "mode": "live",
  "apiVersion": "2026-05-25",
  "data": {
    "subscriptionId": "sub_1a2b3c4d",
    "customerId": "user_123",
    "card": {
      "brand": "visa",
      "last4": "4242",
      "expMonth": 12,
      "expYear": 2030
    }
  }
}

When this fires

Fired when Commet records a payment method for a subscription: after a paid checkout, when a trial starts with a card on file, or when a zero-total checkout completes with a saved payment method.

The card object carries display metadata only — brand, last 4 digits, and expiration. Full card numbers never leave the payment provider. When the saved method is not a card or its details cannot be retrieved, card is null.

Use it to show the saved card in your own billing UI or confirm to the customer that their payment method is on file.