diff --git a/spec/openapi.yaml b/spec/openapi.yaml
index a734901..c7d6dc6 100644
--- a/spec/openapi.yaml
+++ b/spec/openapi.yaml
@@ -391,6 +391,7 @@ tags:
         "date_received":"2016-11-03T11:49:02.807Z",
         "status":"delivered",
         "delay":0,
+        "billing_units":1,
         "submitted_date":"2016-11-03T11:49:01.551Z",
         "original_text":"Hello world!",
         "message_id":"389dc1a8-62a4-4110-ba61-af94806c006f",
@@ -431,6 +432,8 @@ tags:
         * `failed`: The message has failed. Reasons may include no active routes to destination or undeliverable by downstream provider.
 
       * **Delay**: _Deprecated, no longer in use_
+      
+      * **Billing Units**: The number of billing units charged for the message.
 
       * **Submitted Date**: Date time status of the message changed in UTC. For a delivered DR this may indicate the time at which the message was received on the handset.
 
@@ -2084,7 +2087,7 @@ paths:
                     "date_received": "2017-05-20T06:30:37.642Z",
                     "status": "enroute",
                     "delay": 0,
-                    "billing_units": 0,
+                    "billing_units": 1,
                     "submitted_date": "2017-05-20T06:30:37.639Z",
                     "original_text": "My first message!",
                     "message_id": "d781dcab-d9d8-4fb2-9e03-872f07ae94ba",
@@ -2104,7 +2107,7 @@ paths:
                     "date_received": "2017-05-21T01:46:42.579Z",
                     "status": "enroute",
                     "delay": 0,
-                    "billing_units": 0,
+                    "billing_units": 1,
                     "submitted_date": "2017-05-21T01:46:42.574Z",
                     "original_text": "My second message!",
                     "message_id": "fbb3b3f5-b702-4d8b-ab44-65b2ee39a281",
@@ -6707,6 +6710,7 @@ components:
             date_received: '2017-05-20T06:30:37.642Z'
             status: enroute
             delay: 0
+            billing_units: 1
             submitted_date: '2017-05-20T06:30:37.639Z'
             original_text: My first message!
             message_id: d781dcab-d9d8-4fb2-9e03-872f07ae94ba
@@ -6722,6 +6726,7 @@ components:
             date_received: '2017-05-21T01:46:42.579Z'
             status: submitted
             delay: 0
+            billing_units: 1
             submitted_date: '2017-05-21T01:46:42.574Z'
             original_text: My second message!
             message_id: fbb3b3f5-b702-4d8b-ab44-65b2ee39a281