billing.tier_upgraded

project_id is always null for billing events.

When this fires

The creator switches their MemberPass subscription to a higher-priced tier. Pro-ration is applied through the payment provider.

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": "cre_01HX...",
    "from_tier": "starter",
    "to_tier": "growth",
    "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 ULID	Creator whose tier changed.
`data.from_tier`	string	Previous tier slug.
`data.to_tier`	string	New tier slug.
`data.effective_at`	ISO 8601 timestamp	When the new tier took effect.

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.

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