billing.tier_upgraded

project_id is always null for billing events.

When this fires

The creator switches their Subscriby subscription to a higher-priced tier. Pro-ration is applied through the payment provider — except when the creator is still inside their platform trial, where the switch is not prorated because nothing has been paid yet.

Required ability

billing:read — token must carry this at mint time to subscribe an endpoint to this event.

Payload

{
  "id": "evt_01HX...",
  "type": "billing.tier_upgraded",
  "created_at": "2026-05-18T10:05:00Z",
  "api_version": "2026-05-01",
  "project_id": null,
  "data": {
    "creator_id": "2a91c4e7-6f38-4b52-8e0d-9c1a7b3f5d80",
    "from_tier": "308eb3da-1eb6-11f0-b4f2-d8bbc173f8c3",
    "to_tier": "882b72bb-1eb6-11f0-b4f2-d8bbc173f8c3",
    "effective_at": "2026-05-18T10:05:00Z"
  }
}

Field reference

Field	Type	Notes
`id`	string ULID	Unique event id, prefixed `evt_`. Use for idempotent processing.
`type`	string	Always `billing.tier_upgraded` for this event.
`created_at`	ISO 8601 timestamp	Server-side emission time.
`api_version`	string	Webhook API contract version.
`project_id`	null	Always `null` — account-level event.
`data.creator_id`	string UUID	Creator whose tier changed.
`data.from_tier`	string UUID	Previous tier plan id. Always present — a first subscription goes through checkout and emits no tier event.
`data.to_tier`	string UUID	New tier plan id.
`data.effective_at`	ISO 8601 timestamp	Always the emission time — upgrades take effect immediately.

Caveats

Tier changes can unlock features (e.g. Teams on Growth+); event consumers should refresh tier caches on receipt.
Pro-ration charges fire billing.invoice_created separately for the proration line (not on an upgrade taken during the platform trial).

billing.tier_downgraded — opposite direction.
billing.invoice_created — proration invoice.
Billing events overview — back to family overview.