diff --git a/tienda_ilusion/don_confiao/serializers.py b/tienda_ilusion/don_confiao/serializers.py
index 8c68dd4..73426ab 100644
--- a/tienda_ilusion/don_confiao/serializers.py
+++ b/tienda_ilusion/don_confiao/serializers.py
@@ -27,7 +27,7 @@ class ProductSerializer(serializers.ModelSerializer):
 class CustomerSerializer(serializers.ModelSerializer):
     class Meta:
         model = Customer
-        fields = ['id', 'name', 'address', 'email', 'phone']
+        fields = ['id', 'name', 'address', 'email', 'phone', 'external_id']
 
 
 class ReconciliationJarSerializer(serializers.ModelSerializer):
diff --git a/tienda_ilusion/don_confiao/tests/test_api.py b/tienda_ilusion/don_confiao/tests/test_api.py
index 30bd4e0..7ba1b6d 100644
--- a/tienda_ilusion/don_confiao/tests/test_api.py
+++ b/tienda_ilusion/don_confiao/tests/test_api.py
@@ -16,7 +16,8 @@ class TestAPI(APITestCase):
             measuring_unit='UNIT'
         )
         self.customer = Customer.objects.create(
-            name='Camilo'
+            name='Camilo',
+            external_id='18'
         )
 
     def test_create_sale(self):
@@ -67,6 +68,7 @@ class TestAPI(APITestCase):
         json_response = json.loads(response.content.decode('utf-8'))
         self.assertEqual(response.status_code, 200)
         self.assertEqual(self.customer.name, json_response[0]['name'])
+        self.assertEqual(self.customer.external_id, json_response[0]['external_id'])
 
     def test_get_sales_for_tryton(self):
         url = '/don_confiao/api/sales/for_tryton'