diff --git a/quickbooks/client.py b/quickbooks/client.py
index a428044..7ff1943 100644
--- a/quickbooks/client.py
+++ b/quickbooks/client.py
@@ -29,6 +29,7 @@ class QuickBooks(object):
     verifier_token = None
     invoice_link = False
     use_decimal = False
+    include_custom_fields = False
 
     sandbox_api_url_v3 = "https://sandbox-quickbooks.api.intuit.com/v3"
     api_url_v3 = "https://quickbooks.api.intuit.com/v3"
@@ -98,6 +99,8 @@ def __new__(cls, **kwargs):
         if 'use_decimal' in kwargs:
             instance.use_decimal = kwargs.get('use_decimal')
 
+        instance.include_custom_fields = kwargs.get('include_custom_fields', False)
+
         return instance
 
     def _start_session(self):
@@ -163,7 +166,10 @@ def make_request(self, request_type, url, request_body=None, content_type='appli
             params = {}
 
         params['minorversion'] = self.minorversion
-        
+
+        if self.include_custom_fields:
+            params['include'] = 'enhancedAllCustomFields'
+
         if request_id:
             params['requestid'] = request_id
 
diff --git a/tests/unit/test_client.py b/tests/unit/test_client.py
index 94b1eff..39691e3 100644
--- a/tests/unit/test_client.py
+++ b/tests/unit/test_client.py
@@ -173,9 +173,23 @@ def test_make_request(self, process_request):
 
         process_request.assert_called_with(
                 "GET", url, data={},
-                headers={'Content-Type': 'application/json', 'Accept': 'application/json', 'User-Agent': 'python-quickbooks V3 library'}, 
+                headers={'Content-Type': 'application/json', 'Accept': 'application/json', 'User-Agent': 'python-quickbooks V3 library'},
                 params={'minorversion': client.QuickBooks.MINIMUM_MINOR_VERSION})
 
+    @patch('quickbooks.client.QuickBooks.process_request')
+    def test_make_request_without_custom_fields(self, process_request):
+        process_request.return_value = MockResponseJson()
+
+        qb_client = client.QuickBooks(include_custom_fields=True)
+        qb_client.company_id = "1234"
+        url = "https://sandbox-quickbooks.api.intuit.com/v3/company/1234/test/1/"
+        qb_client.make_request("GET", url, request_body=None, content_type='application/json')
+
+        process_request.assert_called_with(
+                "GET", url, data={},
+                headers={'Content-Type': 'application/json', 'Accept': 'application/json', 'User-Agent': 'python-quickbooks V3 library'},
+                params={'minorversion': client.QuickBooks.MINIMUM_MINOR_VERSION, 'include': 'enhancedAllCustomFields'})
+
     def test_handle_exceptions(self):
         qb_client = client.QuickBooks()
         error_data = {
@@ -247,11 +261,11 @@ def test_make_request_file_closed(self, process_request):
         process_request.return_value = MockResponseJson()
         with patch('builtins.open', mock_open(read_data=b'file content')) as mock_file:
             qb_client = client.QuickBooks(auth_client=self.auth_client)
-            qb_client.make_request('POST', 
-                                   'https://sandbox-quickbooks.api.intuit.com/v3/company/COMPANY_ID/attachable', 
-                                   request_body='{"ContentType": "text/plain"}', 
+            qb_client.make_request('POST',
+                                   'https://sandbox-quickbooks.api.intuit.com/v3/company/COMPANY_ID/attachable',
+                                   request_body='{"ContentType": "text/plain"}',
                                    file_path=file_path)
-            
+
             mock_file.assert_called_once_with(file_path, 'rb')
             mock_file.return_value.__enter__.return_value.read.assert_called_once()
             mock_file.return_value.__exit__.assert_called_once()