diff --git a/tienda_ilusion/don_confiao/serializers.py b/tienda_ilusion/don_confiao/serializers.py
index 8c68dd4..923befe 100644
--- a/tienda_ilusion/don_confiao/serializers.py
+++ b/tienda_ilusion/don_confiao/serializers.py
@@ -15,7 +15,7 @@ class SaleSerializer(serializers.ModelSerializer):
     class Meta:
         model = Sale
         fields = ['id', 'customer', 'date', 'saleline_set',
-                  'total', 'payment_method']
+                  'total', 'payment_method', 'external_id']
 
 
 class ProductSerializer(serializers.ModelSerializer):
@@ -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..e9c59dc 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 +68,23 @@ 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(self):
+        url = '/don_confiao/api/sales/'
+        self._create_sale()
+
+        response = self.client.get(url)
+        json_response = json.loads(response.content.decode('utf-8'))
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(self.customer.id, json_response[0]['customer'])
+        self.assertEqual(
+            None,
+            json_response[0]['external_id']
+        )
 
     def test_get_sales_for_tryton(self):
         url = '/don_confiao/api/sales/for_tryton'