diff --git a/CHANGELOG.md b/CHANGELOG.md
index b8413d5..834b8d3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## 0.4.0
+
+- Add `groundEndOfDayClose(closeRequest, options)` — calls the FedEx Ground End of Day Close API (`PUT /ship/v1/endofday/`). Same passthrough pattern as the other methods: caller supplies the full request body, the package forwards it verbatim. Supports `options.customer_transaction_id` and `options.timeout`. Non-2xx responses and 200-with-`errors[]` envelopes both reject with `HttpError`.
+
 ## 0.3.0
 
 - Add `createShipment(shipRequest, options)` — calls the FedEx Ship API to create a shipment (`POST /ship/v1/shipments`). Same passthrough pattern as the other methods: caller supplies the full request body, the package forwards it verbatim. Supports `options.customer_transaction_id` and `options.timeout`. Non-2xx responses and 200-with-`errors[]` envelopes both reject with `HttpError`.
diff --git a/README.md b/README.md
index 47d5930..57f31aa 100644
--- a/README.md
+++ b/README.md
@@ -5,7 +5,7 @@
 [![npm version](https://img.shields.io/npm/v/@stores.com/fedex)](https://www.npmjs.com/package/@stores.com/fedex)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](LICENSE)
 
-FedEx REST API client for Address Validation, OAuth tokens, Rates and Transit Times, Shipment Cancellation, and Shipment Creation.
+FedEx REST API client for Address Validation, Ground End of Day Close, OAuth tokens, Rates and Transit Times, Shipment Cancellation, and Shipment Creation.
 
 ## Installation
 
@@ -128,6 +128,23 @@ console.log(accessToken);
 // }
 ```
 
+### groundEndOfDayClose(closeRequest, options)
+
+Close out FedEx Ground shipments via the Ground End of Day Close API. The caller supplies the full request body — `accountNumber`, `closeDate`, `closeReqType`, `groundServiceCategory` — and the package forwards it verbatim.
+
+See: https://developer.fedex.com/api/en-us/catalog/close/v1/docs.html
+
+```javascript
+const json = await fedex.groundEndOfDayClose({
+    accountNumber: { value: 'your_account_number' },
+    closeDate: '2026-05-14',
+    closeReqType: 'GCDR',
+    groundServiceCategory: 'GROUND'
+});
+```
+
+Non-2xx responses reject with `HttpError`. If FedEx returns a 200 response carrying a non-empty `errors[]` envelope, the call rejects with an `HttpError` whose message is every `message` joined by `; ` and whose `.json` is the full response body (with the `errors[]` array, codes, and any other fields).
+
 ### rateAndTransitTimes(rateRequest, options)
 
 Request rate quotes and transit times from FedEx. The caller supplies the full request body — `accountNumber`, `requestedShipment`, and any of `rateRequestControlParameters`, `carrierCodes`, `processingOptions`, `version` — and the package forwards it verbatim.
diff --git a/index.js b/index.js
index 194500e..aaea905 100644
--- a/index.js
+++ b/index.js
@@ -139,6 +139,52 @@ function FedEx(args) {
         return json;
     };
 
+    /**
+     * Close out FedEx Ground shipments via the Ground End of Day Close API. The
+     * caller supplies the full request body — `accountNumber`, `closeDate`,
+     * `closeReqType`, `groundServiceCategory` — and the package forwards it
+     * verbatim.
+     *
+     * @param {object} closeRequest - Full Ground End of Day Close request body.
+     * @param {object} [options]
+     * @param {string} [options.customer_transaction_id] - Sent as the `x-customer-transaction-id`
+     *   request header. FedEx echoes this back so callers can correlate requests with responses.
+     * @param {number} [options.timeout=30000] - Request timeout in milliseconds.
+     * @returns {Promise<object>} The parsed response body, including `output.closeDocuments[]`.
+     * @see https://developer.fedex.com/api/en-us/catalog/close/v1/docs.html
+     */
+    this.groundEndOfDayClose = async (closeRequest, options = {}) => {
+        const accessToken = await this.getAccessToken();
+
+        const headers = {
+            Authorization: `Bearer ${accessToken.access_token}`,
+            'Content-Type': 'application/json'
+        };
+
+        if (options.customer_transaction_id) {
+            headers['x-customer-transaction-id'] = options.customer_transaction_id;
+        }
+
+        const response = await fetch(`${_options.url}/ship/v1/endofday/`, {
+            body: JSON.stringify(closeRequest),
+            headers,
+            method: 'PUT',
+            signal: AbortSignal.timeout(options.timeout || 30000)
+        });
+
+        if (!response.ok) {
+            throw await HttpError.from(response);
+        }
+
+        const json = await response.json();
+
+        if (json.errors?.length) {
+            throw await HttpError.from(response);
+        }
+
+        return json;
+    };
+
     /**
      * Call the FedEx Rates and Transit Times API. The caller supplies the full request body
      * — `accountNumber`, `requestedShipment`, and any of `rateRequestControlParameters`,
diff --git a/package.json b/package.json
index 7aac9a6..a612a8a 100644
--- a/package.json
+++ b/package.json
@@ -3,7 +3,7 @@
         "@stores.com/http-error": "~1.1.0",
         "memory-cache": "~0.2.0"
     },
-    "description": "FedEx REST API client for address validation, OAuth tokens, rate quotes, shipment cancellation, and shipment creation.",
+    "description": "FedEx REST API client for address validation, ground end of day close, OAuth tokens, rate quotes, shipment cancellation, and shipment creation.",
     "devDependencies": {
         "@eslint/js": "*",
         "async": "~3.2.0",
@@ -14,6 +14,7 @@
         "cancel",
         "create",
         "fedex",
+        "ground-end-of-day-close",
         "logistics",
         "rates",
         "ship",
@@ -33,5 +34,5 @@
         "test": "node --test --test-force-exit --test-reporter=spec",
         "test:only": "node --test --test-force-exit --test-only --test-reporter=spec"
     },
-    "version": "0.3.0"
+    "version": "0.4.0"
 }
diff --git a/test/index.js b/test/index.js
index b8f2abb..4a906a6 100644
--- a/test/index.js
+++ b/test/index.js
@@ -404,6 +404,171 @@ test('getAccessToken', { concurrency: true }, async (t) => {
     });
 });
 
+test('groundEndOfDayClose', { concurrency: true }, async (t) => {
+    t.test('should close ground shipments', async () => {
+        const fedex = new FedEx({
+            api_key: process.env.FEDEX_API_KEY,
+            secret_key: process.env.FEDEX_SECRET_KEY,
+            url: process.env.FEDEX_URL
+        });
+
+        const body = await async.retry(async () => fedex.groundEndOfDayClose({
+            accountNumber: { value: process.env.FEDEX_ACCOUNT_NUMBER },
+            closeDate: new Date().toISOString().slice(0, 10),
+            closeReqType: 'GCDR',
+            groundServiceCategory: 'GROUND'
+        }));
+
+        assert(body);
+        assert(body.transactionId);
+    });
+});
+
+test('groundEndOfDayClose (mocked)', async (t) => {
+    t.test('should forward close request body verbatim', async (t) => {
+        let sentBody;
+
+        t.mock.method(globalThis, 'fetch', async (url, init) => {
+            if (url.endsWith('/oauth/token')) {
+                return new Response(JSON.stringify({ access_token: 'mock', expires_in: 3600, token_type: 'bearer' }), {
+                    headers: { 'Content-Type': 'application/json' },
+                    status: 200
+                });
+            }
+
+            if (url.endsWith('/ship/v1/endofday/')) {
+                sentBody = JSON.parse(init.body);
+                return new Response(JSON.stringify({ output: { closeDocuments: [] }, transactionId: 'mock' }), {
+                    headers: { 'Content-Type': 'application/json' },
+                    status: 200
+                });
+            }
+
+            throw new Error(`Unexpected fetch URL: ${url}`);
+        });
+
+        const fedex = new FedEx({ api_key: 'mock', secret_key: 'mock' });
+
+        await fedex.groundEndOfDayClose({
+            accountNumber: { value: '123456789' },
+            closeDate: '2026-05-14',
+            closeReqType: 'GCDR',
+            groundServiceCategory: 'GROUND'
+        });
+
+        assert.deepStrictEqual(sentBody, {
+            accountNumber: { value: '123456789' },
+            closeDate: '2026-05-14',
+            closeReqType: 'GCDR',
+            groundServiceCategory: 'GROUND'
+        });
+    });
+
+    t.test('should send options.customer_transaction_id as x-customer-transaction-id header and use PUT method', async (t) => {
+        let sentHeader;
+        let sentMethod;
+
+        t.mock.method(globalThis, 'fetch', async (url, init) => {
+            if (url.endsWith('/oauth/token')) {
+                return new Response(JSON.stringify({ access_token: 'mock', expires_in: 3600, token_type: 'bearer' }), {
+                    headers: { 'Content-Type': 'application/json' },
+                    status: 200
+                });
+            }
+
+            if (url.endsWith('/ship/v1/endofday/')) {
+                sentHeader = init.headers['x-customer-transaction-id'];
+                sentMethod = init.method;
+                return new Response(JSON.stringify({ output: { closeDocuments: [] }, transactionId: 'mock' }), {
+                    headers: { 'Content-Type': 'application/json' },
+                    status: 200
+                });
+            }
+
+            throw new Error(`Unexpected fetch URL: ${url}`);
+        });
+
+        const fedex = new FedEx({ api_key: 'mock', secret_key: 'mock' });
+
+        await fedex.groundEndOfDayClose({
+            accountNumber: { value: process.env.FEDEX_ACCOUNT_NUMBER },
+            closeDate: '2026-05-14',
+            closeReqType: 'GCDR',
+            groundServiceCategory: 'GROUND'
+        }, { customer_transaction_id: 'abc-123' });
+
+        assert.strictEqual(sentHeader, 'abc-123');
+        assert.strictEqual(sentMethod, 'PUT');
+    });
+
+    t.test('should throw HttpError for 200 response with errors envelope', async (t) => {
+        t.mock.method(globalThis, 'fetch', async (url) => {
+            if (url.endsWith('/oauth/token')) {
+                return new Response(JSON.stringify({ access_token: 'mock', expires_in: 3600, token_type: 'bearer' }), {
+                    headers: { 'Content-Type': 'application/json' },
+                    status: 200
+                });
+            }
+
+            if (url.endsWith('/ship/v1/endofday/')) {
+                return new Response(JSON.stringify({
+                    errors: [
+                        { code: 'CLOSE.FAILURE', message: 'No shipments to close' }
+                    ],
+                    transactionId: 'mock'
+                }), {
+                    headers: { 'Content-Type': 'application/json' },
+                    status: 200
+                });
+            }
+
+            throw new Error(`Unexpected fetch URL: ${url}`);
+        });
+
+        const fedex = new FedEx({ api_key: 'mock', secret_key: 'mock' });
+
+        await assert.rejects(fedex.groundEndOfDayClose({
+            accountNumber: { value: process.env.FEDEX_ACCOUNT_NUMBER },
+            closeDate: '2026-05-14',
+            closeReqType: 'GCDR',
+            groundServiceCategory: 'GROUND'
+        }), (err) => {
+            assert.strictEqual(err.name, 'HttpError');
+            return true;
+        });
+    });
+
+    t.test('should throw HttpError for non 2xx response', async (t) => {
+        t.mock.method(globalThis, 'fetch', async (url) => {
+            if (url.endsWith('/oauth/token')) {
+                return new Response(JSON.stringify({ access_token: 'mock', expires_in: 3600, token_type: 'bearer' }), {
+                    headers: { 'Content-Type': 'application/json' },
+                    status: 200
+                });
+            }
+
+            if (url.endsWith('/ship/v1/endofday/')) {
+                return new Response('', { status: 500, statusText: 'Internal Server Error' });
+            }
+
+            throw new Error(`Unexpected fetch URL: ${url}`);
+        });
+
+        const fedex = new FedEx({ api_key: 'mock', secret_key: 'mock' });
+
+        await assert.rejects(fedex.groundEndOfDayClose({
+            accountNumber: { value: process.env.FEDEX_ACCOUNT_NUMBER },
+            closeDate: '2026-05-14',
+            closeReqType: 'GCDR',
+            groundServiceCategory: 'GROUND'
+        }), (err) => {
+            assert.strictEqual(err.name, 'HttpError');
+            assert.match(err.message, /^500/);
+            return true;
+        });
+    });
+});
+
 test('rateAndTransitTimes', { concurrency: true }, async (t) => {
     t.test('should return rate quotes for a Ground shipment', async () => {
         const fedex = new FedEx({