diff --git a/functions/billing_stop_on_notification/requirements-test.txt b/functions/billing_stop_on_notification/requirements-test.txt
new file mode 100644
index 0000000000..66801836e2
--- /dev/null
+++ b/functions/billing_stop_on_notification/requirements-test.txt
@@ -0,0 +1,2 @@
+pytest==8.3.5
+cloudevents==1.11.0
\ No newline at end of file
diff --git a/functions/billing_stop_on_notification/requirements.txt b/functions/billing_stop_on_notification/requirements.txt
new file mode 100644
index 0000000000..912b07cd0a
--- /dev/null
+++ b/functions/billing_stop_on_notification/requirements.txt
@@ -0,0 +1,3 @@
+functions-framework==3.*
+google-cloud-billing==1.16.2
+google-cloud-logging==3.12.1
diff --git a/functions/billing_stop_on_notification/stop_billing.py b/functions/billing_stop_on_notification/stop_billing.py
new file mode 100644
index 0000000000..fcb6563e05
--- /dev/null
+++ b/functions/billing_stop_on_notification/stop_billing.py
@@ -0,0 +1,169 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the 'License');
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an 'AS IS' BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# [START functions_billing_stop]
+# WARNING: The following action, if not in simulation mode, will disable billing
+# for the project, potentially stopping all services and causing outages.
+# Ensure thorough testing and understanding before enabling live deactivation.
+
+import base64
+import json
+import os
+import urllib.request
+
+from cloudevents.http.event import CloudEvent
+import functions_framework
+
+from google.api_core import exceptions
+from google.cloud import billing_v1
+from google.cloud import logging
+
+billing_client = billing_v1.CloudBillingClient()
+
+
+def get_project_id() -> str:
+    """Retrieves the Google Cloud Project ID.
+
+    This function first attempts to get the project ID from the
+    `GOOGLE_CLOUD_PROJECT` environment variable. If the environment
+    variable is not set or is None, it then attempts to retrieve the
+    project ID from the Google Cloud metadata server.
+
+    Returns:
+        str: The Google Cloud Project ID.
+
+    Raises:
+        ValueError: If the project ID cannot be determined either from
+                    the environment variable or the metadata server.
+    """
+
+    # Read the environment variable, usually set manually
+    project_id = os.getenv("GOOGLE_CLOUD_PROJECT")
+    if project_id is not None:
+        return project_id
+
+    # Otherwise, get the `project-id`` from the Metadata server
+    url = "http://metadata.google.internal/computeMetadata/v1/project/project-id"
+    req = urllib.request.Request(url)
+    req.add_header("Metadata-Flavor", "Google")
+    project_id = urllib.request.urlopen(req).read().decode()
+
+    if project_id is None:
+        raise ValueError("project-id metadata not found.")
+
+    return project_id
+
+
+@functions_framework.cloud_event
+def stop_billing(cloud_event: CloudEvent) -> None:
+    # TODO(developer): As stoping billing is a destructive action
+    # for your project, change the following constant to False
+    # after you validate with a test budget.
+    SIMULATE_DEACTIVATION = True
+
+    PROJECT_ID = get_project_id()
+    PROJECT_NAME = f"projects/{PROJECT_ID}"
+
+    event_data = base64.b64decode(
+        cloud_event.data["message"]["data"]
+    ).decode("utf-8")
+
+    event_dict = json.loads(event_data)
+    cost_amount = event_dict["costAmount"]
+    budget_amount = event_dict["budgetAmount"]
+    print(f"Cost: {cost_amount} Budget: {budget_amount}")
+
+    if cost_amount <= budget_amount:
+        print("No action required. Current cost is within budget.")
+        return
+
+    print(f"Disabling billing for project '{PROJECT_NAME}'...")
+
+    is_billing_enabled = _is_billing_enabled(PROJECT_NAME)
+
+    if is_billing_enabled:
+        _disable_billing_for_project(
+            PROJECT_NAME,
+            SIMULATE_DEACTIVATION
+        )
+    else:
+        print("Billing is already disabled.")
+
+
+def _is_billing_enabled(project_name: str) -> bool:
+    """Determine whether billing is enabled for a project.
+
+    Args:
+        project_name: Name of project to check if billing is enabled.
+
+    Returns:
+        Whether project has billing enabled or not.
+    """
+    try:
+        print(f"Getting billing info for project '{project_name}'...")
+        response = billing_client.get_project_billing_info(name=project_name)
+
+        return response.billing_enabled
+    except Exception as e:
+        print(f'Error getting billing info: {e}')
+        print(
+            "Unable to determine if billing is enabled on specified project, "
+            "assuming billing is enabled."
+        )
+
+        return True
+
+
+def _disable_billing_for_project(
+    project_name: str,
+    simulate_deactivation: bool,
+) -> None:
+    """Disable billing for a project by removing its billing account.
+
+    Args:
+        project_name: Name of project to disable billing.
+        simulate_deactivation:
+            If True, it won't actually disable billing.
+            Useful to validate with test budgets.
+    """
+
+    # Log this operation in Cloud Logging
+    logging_client = logging.Client()
+    logger = logging_client.logger(name="disable-billing")
+
+    if simulate_deactivation:
+        entry_text = "Billing disabled. (Simulated)"
+        print(entry_text)
+        logger.log_text(entry_text, severity="CRITICAL")
+        return
+
+    # Find more information about `updateBillingInfo` API method here:
+    # https://cloud.google.com/billing/docs/reference/rest/v1/projects/updateBillingInfo
+    try:
+        # To disable billing set the `billing_account_name` field to empty
+        project_billing_info = billing_v1.ProjectBillingInfo(
+            billing_account_name=""
+        )
+
+        response = billing_client.update_project_billing_info(
+            name=project_name,
+            project_billing_info=project_billing_info
+        )
+
+        entry_text = f"Billing disabled: {response}"
+        print(entry_text)
+        logger.log_text(entry_text, severity="CRITICAL")
+    except exceptions.PermissionDenied:
+        print("Failed to disable billing, check permissions.")
+# [END functions_billing_stop]
diff --git a/functions/billing_stop_on_notification/stop_billing_test.py b/functions/billing_stop_on_notification/stop_billing_test.py
new file mode 100644
index 0000000000..5ad4f9f3bf
--- /dev/null
+++ b/functions/billing_stop_on_notification/stop_billing_test.py
@@ -0,0 +1,83 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the 'License');
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an 'AS IS' BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import base64
+import json
+
+from cloudevents.conversion import to_structured
+from cloudevents.http import CloudEvent
+
+from flask.testing import FlaskClient
+
+from functions_framework import create_app
+
+import pytest
+
+
+@pytest.fixture
+def cloud_event_budget_alert() -> CloudEvent:
+    attributes = {
+        "specversion": "1.0",
+        "id": "my-id",
+        "source": "//pubsub.googleapis.com/projects/PROJECT_NAME/topics/TOPIC_NAME",
+        "type": "google.cloud.pubsub.topic.v1.messagePublished",
+        "datacontenttype": "application/json",
+        "time": "2025-05-09T18:32:46.572Z"
+    }
+
+    budget_data = {
+        "budgetDisplayName": "BUDGET_NAME",
+        "alertThresholdExceeded": 1.0,
+        "costAmount": 2.0,
+        "costIntervalStart": "2025-05-01T07:00:00Z",
+        "budgetAmount": 0.01,
+        "budgetAmountType": "SPECIFIED_AMOUNT",
+        "currencyCode": "USD"
+    }
+
+    json_string = json.dumps(budget_data)
+    message_base64 = base64.b64encode(json_string.encode('utf-8')).decode('utf-8')
+
+    data = {
+        "message": {
+            "data": message_base64
+        }
+    }
+
+    return CloudEvent(attributes, data)
+
+
+@pytest.fixture
+def client() -> FlaskClient:
+    source = "stop_billing.py"
+    target = "stop_billing"
+    return create_app(target, source, "cloudevent").test_client()
+
+
+def test_receive_notification_to_stop_billing(
+    client: FlaskClient,
+    cloud_event_budget_alert: CloudEvent,
+    capsys: pytest.CaptureFixture[str]
+) -> None:
+    headers, data = to_structured(cloud_event_budget_alert)
+    resp = client.post("/", headers=headers, data=data)
+
+    captured = capsys.readouterr()
+
+    assert resp.status_code == 200
+    assert resp.data == b"OK"
+
+    assert "Getting billing info for project" in captured.out
+    assert "Disabling billing for project" in captured.out
+    assert "Billing disabled. (Simulated)" in captured.out