diff --git a/functions/billing/stop_billing/.gcloudignore b/functions/billing/stop_billing/.gcloudignore
new file mode 100644
index 0000000000..ccc4eb240e
--- /dev/null
+++ b/functions/billing/stop_billing/.gcloudignore
@@ -0,0 +1,16 @@
+# This file specifies files that are *not* uploaded to Google Cloud Platform
+# using gcloud. It follows the same syntax as .gitignore, with the addition of
+# "#!include" directives (which insert the entries of the given .gitignore-style
+# file at that point).
+#
+# For more information, run:
+#   $ gcloud topic gcloudignore
+#
+.gcloudignore
+# If you would like to upload your .git directory, .gitignore file or files
+# from your .gitignore file, remove the corresponding line
+# below:
+.git
+.gitignore
+
+node_modules
diff --git a/functions/billing/stop_billing/index.js b/functions/billing/stop_billing/index.js
new file mode 100644
index 0000000000..204780ff5a
--- /dev/null
+++ b/functions/billing/stop_billing/index.js
@@ -0,0 +1,117 @@
+// 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]
+const {CloudBillingClient} = require('@google-cloud/billing');
+const functions = require('@google-cloud/functions-framework');
+const gcpMetadata = require('gcp-metadata');
+
+const billing = new CloudBillingClient();
+
+functions.cloudEvent('stopBilling', async cloudEvent => {
+  // TODO(developer): As stopping billing is a destructive action
+  // for your project, change the following constant to false
+  // after you validate with a test budget.
+  const simulateDeactivation = true;
+
+  let projectId;
+
+  try {
+    projectId = await gcpMetadata.project('project-id');
+  } catch (error) {
+    console.error('project-id metadata not found:', error);
+    return;
+  }
+
+  const projectName = `projects/${projectId}`;
+
+  const eventData = Buffer.from(
+    cloudEvent.data['message']['data'],
+    'base64'
+  ).toString();
+
+  const eventObject = JSON.parse(eventData);
+
+  console.log(
+    `Cost: ${eventObject.costAmount} Budget: ${eventObject.budgetAmount}`
+  );
+
+  if (eventObject.costAmount <= eventObject.budgetAmount) {
+    console.log('No action required. Current cost is within budget.');
+    return;
+  }
+
+  console.log(`Disabling billing for project '${projectName}'...`);
+
+  const billingEnabled = await _isBillingEnabled(projectName);
+  if (billingEnabled) {
+    _disableBillingForProject(projectName, simulateDeactivation);
+  } else {
+    console.log('Billing is already disabled.');
+  }
+});
+
+/**
+ * Determine whether billing is enabled for a project
+ * @param {string} projectName The name of the project to check
+ * @returns {boolean} Whether the project has billing enabled or not
+ */
+const _isBillingEnabled = async projectName => {
+  try {
+    console.log(`Getting billing info for project '${projectName}'...`);
+    const [res] = await billing.getProjectBillingInfo({name: projectName});
+
+    return res.billingEnabled;
+  } catch (e) {
+    console.log('Error getting billing info:', e);
+    console.log(
+      'Unable to determine if billing is enabled on specified project, ' +
+        'assuming billing is enabled'
+    );
+
+    return true;
+  }
+};
+
+/**
+ * Disable billing for a project by removing its billing account
+ * @param {string} projectName The name of the project to disable billing
+ * @param {boolean} simulateDeactivation
+ *   If true, it won't actually disable billing.
+ *   Useful to validate with test budgets.
+ * @returns {void}
+ */
+const _disableBillingForProject = async (projectName, simulateDeactivation) => {
+  if (simulateDeactivation) {
+    console.log('Billing disabled. (Simulated)');
+    return;
+  }
+
+  // Find more information about `projects/updateBillingInfo` API method here:
+  // https://cloud.google.com/billing/docs/reference/rest/v1/projects/updateBillingInfo
+  try {
+    // To disable billing set the `billingAccountName` field to empty
+    const requestBody = {billingAccountName: ''};
+
+    const [response] = await billing.updateProjectBillingInfo({
+      name: projectName,
+      resource: requestBody,
+    });
+
+    console.log(`Billing disabled: ${JSON.stringify(response)}`);
+  } catch (e) {
+    console.log('Failed to disable billing, check permissions.', e);
+  }
+};
+// [END functions_billing_stop]
diff --git a/functions/billing/stop_billing/package.json b/functions/billing/stop_billing/package.json
new file mode 100644
index 0000000000..c3bc9fb60c
--- /dev/null
+++ b/functions/billing/stop_billing/package.json
@@ -0,0 +1,30 @@
+{
+  "name": "cloud-functions-stop-billing",
+  "private": "true",
+  "version": "0.0.1",
+  "description": "Disable billing with a budget notification.",
+  "main": "index.js",
+  "engines": {
+    "node": ">=20.0.0"
+  },
+  "scripts": {
+    "compute-test": "c8 mocha -p -j 2 test/periodic.test.js --timeout=600000",
+    "test": "c8 mocha -p -j 2 test/index.test.js --timeout=5000 --exit"
+  },
+  "author": "Ace Nassri <anassri@google.com>",
+  "license": "Apache-2.0",
+  "dependencies": {
+    "@google-cloud/billing": "^4.0.0",
+    "@google-cloud/functions-framework": "^3.0.0",
+    "gcp-metadata": "^6.0.0"
+  },
+  "devDependencies": {
+    "c8": "^10.0.0",
+    "gaxios": "^6.0.0",
+    "mocha": "^10.0.0",
+    "promise-retry": "^2.0.0",
+    "proxyquire": "^2.1.0",
+    "sinon": "^18.0.0",
+    "wait-port": "^1.0.4"
+  }
+}
diff --git a/functions/billing/stop_billing/test/index.test.js b/functions/billing/stop_billing/test/index.test.js
new file mode 100644
index 0000000000..47328b1d96
--- /dev/null
+++ b/functions/billing/stop_billing/test/index.test.js
@@ -0,0 +1,152 @@
+// Copyright 2019 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.
+
+const {exec} = require('child_process');
+const {request} = require('gaxios');
+const assert = require('assert');
+const sinon = require('sinon');
+const waitPort = require('wait-port');
+const {InstancesClient} = require('@google-cloud/compute');
+const sample = require('../index.js');
+
+const {BILLING_ACCOUNT} = process.env;
+
+describe('functions/billing tests', () => {
+  let projectId;
+  before(async () => {
+    const client = new InstancesClient();
+    projectId = await client.getProjectId();
+  });
+  after(async () => {
+    // Re-enable billing using the sample file itself
+    // Invoking the file directly is more concise vs. re-implementing billing setup here
+    const jsonData = {
+      billingAccountName: `billingAccounts/${BILLING_ACCOUNT}`,
+      projectName: `projects/${projectId}`,
+    };
+    const encodedData = Buffer.from(JSON.stringify(jsonData)).toString(
+      'base64'
+    );
+    const pubsubMessage = {data: encodedData, attributes: {}};
+    await require('../').startBilling(pubsubMessage);
+  });
+
+  describe('notifies Slack', () => {
+    let ffProc;
+    const PORT = 8080;
+    const BASE_URL = `http://localhost:${PORT}`;
+
+    before(async () => {
+      console.log('Starting functions-framework process...');
+      ffProc = exec(
+        `npx functions-framework --target=notifySlack --signature-type=event --port ${PORT}`
+      );
+      await waitPort({host: 'localhost', port: PORT});
+      console.log('functions-framework process started and listening!');
+    });
+
+    after(() => {
+      console.log('Ending functions-framework process...');
+      ffProc.kill();
+      console.log('functions-framework process stopped.');
+    });
+
+    describe('functions_billing_slack', () => {
+      it('should notify Slack when budget is exceeded', async () => {
+        const jsonData = {costAmount: 500, budgetAmount: 400};
+        const encodedData = Buffer.from(JSON.stringify(jsonData)).toString(
+          'base64'
+        );
+        const pubsubMessage = {data: encodedData, attributes: {}};
+
+        const response = await request({
+          url: `${BASE_URL}/notifySlack`,
+          method: 'POST',
+          data: {data: pubsubMessage},
+        });
+
+        assert.strictEqual(response.status, 200);
+        assert.strictEqual(
+          response.data,
+          'Slack notification sent successfully'
+        );
+      });
+    });
+  });
+
+  describe('disables billing', () => {
+    let ffProc;
+    const PORT = 8081;
+    const BASE_URL = `http://localhost:${PORT}`;
+
+    before(async () => {
+      console.log('Starting functions-framework process...');
+      ffProc = exec(
+        `npx functions-framework --target=stopBilling --signature-type=event --port ${PORT}`
+      );
+      await waitPort({host: 'localhost', port: PORT});
+      console.log('functions-framework process started and listening!');
+    });
+
+    after(() => {
+      console.log('Ending functions-framework process...');
+      ffProc.kill();
+      console.log('functions-framework process stopped.');
+    });
+
+    describe('functions_billing_stop', () => {
+      xit('should disable billing when budget is exceeded', async () => {
+        // Use functions framework to ensure sample follows GCF specification
+        // (Invoking it directly works too, but DOES NOT ensure GCF compatibility)
+        const jsonData = {costAmount: 500, budgetAmount: 400};
+        const encodedData = Buffer.from(JSON.stringify(jsonData)).toString(
+          'base64'
+        );
+        const pubsubMessage = {data: encodedData, attributes: {}};
+
+        const response = await request({
+          url: `${BASE_URL}/stopBilling`,
+          method: 'POST',
+          data: {data: pubsubMessage},
+        });
+
+        assert.strictEqual(response.status, 200);
+        assert.ok(response.data.includes('Billing disabled'));
+      });
+    });
+  });
+
+  describe('shuts down GCE instances', () => {
+    describe('functions_billing_limit', () => {
+      it('should attempt to shut down GCE instances when budget is exceeded', async () => {
+        const jsonData = {costAmount: 500, budgetAmount: 400};
+        const encodedData = Buffer.from(JSON.stringify(jsonData)).toString(
+          'base64'
+        );
+        const pubsubMessage = {data: encodedData, attributes: {}};
+        // Mock GCE (because real GCE instances take too long to start/stop)
+        const instances = [{name: 'test-instance-1', status: 'RUNNING'}];
+        const listStub = sinon
+          .stub(sample.getInstancesClient(), 'list')
+          .resolves([instances]);
+        const stopStub = sinon
+          .stub(sample.getInstancesClient(), 'stop')
+          .resolves({});
+        await sample.limitUse(pubsubMessage);
+        assert.strictEqual(listStub.calledOnce, true);
+        assert.ok(stopStub.calledOnce);
+      });
+    });
+  });
+});
diff --git a/functions/billing/stop_billing/test/periodic.test.js b/functions/billing/stop_billing/test/periodic.test.js
new file mode 100644
index 0000000000..1d6496126c
--- /dev/null
+++ b/functions/billing/stop_billing/test/periodic.test.js
@@ -0,0 +1,89 @@
+// Copyright 2019 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.
+
+const {exec} = require('child_process');
+const {request} = require('gaxios');
+const assert = require('assert');
+const promiseRetry = require('promise-retry');
+
+const BASE_URL = process.env.BASE_URL || 'http://localhost:8080';
+
+describe('functions_billing_limit', () => {
+  let ffProc;
+  before(async () => {
+    console.log('Running periodic before hook....');
+    // Re-enable compute instances using the sample file itself
+    const {startInstances, listRunningInstances} = require('../');
+
+    const emptyJson = JSON.stringify({});
+    const encodedData = Buffer.from(emptyJson).toString('base64');
+    const emptyMessage = {data: encodedData, attributes: {}};
+
+    await startInstances(emptyMessage);
+
+    try {
+      await promiseRetry(
+        async (retry, n) => {
+          const result = await listRunningInstances(emptyMessage);
+
+          console.log(`${n}: ${result}`);
+          if (result.length > 0) {
+            return Promise.resolve();
+          } else {
+            return retry();
+          }
+        },
+        {retries: 8}
+      );
+    } catch (err) {
+      console.error('Failed to restart GCE instances:', err);
+    }
+    console.log('Periodic before hook complete.');
+  });
+
+  after(() => {
+    console.log('Ending functions-framework process...');
+    ffProc.kill();
+    console.log('functions-framework process stopped.');
+  });
+
+  it('should shut down GCE instances when budget is exceeded', async () => {
+    console.log('Starting functions-framework process...');
+    ffProc = exec(
+      'npx functions-framework --target=limitUse --signature-type=event'
+    );
+    console.log('functions-framework process started and listening!');
+
+    const jsonData = {costAmount: 500, budgetAmount: 400};
+    const encodedData = Buffer.from(JSON.stringify(jsonData)).toString(
+      'base64'
+    );
+    const pubsubMessage = {data: encodedData, attributes: {}};
+
+    const response = await request({
+      url: `${BASE_URL}/`,
+      method: 'POST',
+      data: {data: pubsubMessage},
+      retryConfig: {
+        retries: 3,
+        retryDelay: 200,
+      },
+    });
+
+    console.log(response.data);
+
+    assert.strictEqual(response.status, 200);
+    assert.ok(response.data.includes('instance(s) stopped successfully'));
+  });
+});