diff --git a/src/Id/Webhooks/EventType.php b/src/Id/Webhooks/EventType.php
index 9a1de68..a1c31a8 100644
--- a/src/Id/Webhooks/EventType.php
+++ b/src/Id/Webhooks/EventType.php
@@ -61,6 +61,21 @@ final class EventType
     /** A checkout session was not confirmed within 24 hours; its drafts were cancelled. */
     public const CHECKOUT_EXPIRED = 'checkout.expired';
 
+    /**
+     * A user's open monthly bill reached their billing limit: start no new paid service for them.
+     * `data.object` is the billing limit as the app reads it (with `version`), `data.reason`
+     * `booking` or `limit_changed`. Opt-in: only endpoints that select this event get it (not
+     * through `*`), and only apps that may read the limit of a user connected to them.
+     */
+    public const BILLING_LIMIT_REACHED = 'billing_limit.reached';
+
+    /**
+     * A user whose billing limit was reached has room again. `data.object` is the billing limit
+     * (with `version`), `data.reason` `limit_changed`, `limit_removed`, `voided`, `period_reset`
+     * or `order_changed`. Opt-in like BILLING_LIMIT_REACHED.
+     */
+    public const BILLING_LIMIT_AVAILABLE = 'billing_limit.available';
+
     public const TEST = 'webhook.test';
 
     /**
diff --git a/tests/Id/WebhookTest.php b/tests/Id/WebhookTest.php
index 5061bb3..2c8b984 100644
--- a/tests/Id/WebhookTest.php
+++ b/tests/Id/WebhookTest.php
@@ -76,6 +76,14 @@ class WebhookTest extends TestCase
         $this->assertContains(EventType::ORDER_REFUNDED, EventType::all());
     }
 
+    public function test_billing_limit_events_have_their_own_types(): void
+    {
+        $this->assertSame('billing_limit.reached', EventType::BILLING_LIMIT_REACHED);
+        $this->assertSame('billing_limit.available', EventType::BILLING_LIMIT_AVAILABLE);
+        $this->assertContains(EventType::BILLING_LIMIT_REACHED, EventType::all());
+        $this->assertContains(EventType::BILLING_LIMIT_AVAILABLE, EventType::all());
+    }
+
     public function test_a_change_carries_the_previous_attributes(): void
     {
         $this->payload = json_encode(['id' => '01JEVT', 'type' => EventType::SUBSCRIPTION_UPDATED, 'created' => time(), 'data' => [