diff --git a/app/celery/tasks.py b/app/celery/tasks.py
index a868a76dc..cdf5dc7d2 100644
--- a/app/celery/tasks.py
+++ b/app/celery/tasks.py
@@ -267,18 +267,23 @@ def persist_letter(
 def build_dvla_file(self, job_id):
     try:
         if all_notifications_are_created_for_job(job_id):
-            notifications = dao_get_all_notifications_for_job(job_id)
-            file = ""
-            for n in notifications:
-                t = {"content": n.template.content, "subject": n.template.subject}
-                # This unique id is a 7 digits requested by DVLA, not known if this number needs to be sequential.
-                unique_id = int(''.join(map(str, random.sample(range(9), 7))))
-                template = LetterDVLATemplate(t, n.personalisation, unique_id)
-                file = file + str(template) + "\n"
-            s3upload(filedata=file,
-                     region=current_app.config['AWS_REGION'],
-                     bucket_name=current_app.config['DVLA_UPLOAD_BUCKET_NAME'],
-                     file_location="{}-dvla-job.text".format(job_id))
+            file_contents = '\n'.join(
+                str(LetterDVLATemplate(
+                    notification.template.__dict__,
+                    notification.personalisation,
+                    # This unique id is a 7 digits requested by DVLA, not known
+                    # if this number needs to be sequential.
+                    numeric_id=random.randint(1, int('9' * 7)),
+                    contact_block=notification.service.letter_contact_block,
+                ))
+                for notification in dao_get_all_notifications_for_job(job_id)
+            )
+            s3upload(
+                filedata=file_contents + '\n',
+                region=current_app.config['AWS_REGION'],
+                bucket_name=current_app.config['DVLA_UPLOAD_BUCKET_NAME'],
+                file_location="{}-dvla-job.text".format(job_id)
+            )
         else:
             current_app.logger.info("All notifications for job {} are not persisted".format(job_id))
             self.retry(queue="retry", exc="All notifications for job {} are not persisted".format(job_id))
diff --git a/tests/app/celery/test_tasks.py b/tests/app/celery/test_tasks.py
index eae030386..671d52189 100644
--- a/tests/app/celery/test_tasks.py
+++ b/tests/app/celery/test_tasks.py
@@ -971,17 +971,30 @@ def test_build_dvla_file(sample_letter_template, mocker):
     create_notification(template=job.template, job=job)
     create_notification(template=job.template, job=job)
 
-    mocked = mocker.patch("app.celery.tasks.s3upload")
-    mocker.patch("app.celery.tasks.LetterDVLATemplate.__str__", return_value="dvla|string")
+    mocker.patch("app.celery.tasks.random.randint", return_value=999)
+    mocked_upload = mocker.patch("app.celery.tasks.s3upload")
+    mocked_letter_template = mocker.patch("app.celery.tasks.LetterDVLATemplate")
+    mocked_letter_template_instance = mocked_letter_template.return_value
+    mocked_letter_template_instance.__str__.return_value = "dvla|string"
     build_dvla_file(job.id)
 
-    file = "dvla|string\ndvla|string\n"
+    mocked_upload.assert_called_once_with(
+        filedata="dvla|string\ndvla|string\n",
+        region=current_app.config['AWS_REGION'],
+        bucket_name=current_app.config['DVLA_UPLOAD_BUCKET_NAME'],
+        file_location="{}-dvla-job.text".format(job.id)
+    )
 
-    assert mocked.called
-    mocked.assert_called_once_with(filedata=file,
-                                   region=current_app.config['AWS_REGION'],
-                                   bucket_name=current_app.config['DVLA_UPLOAD_BUCKET_NAME'],
-                                   file_location="{}-dvla-job.text".format(job.id))
+    # Template
+    assert mocked_letter_template.call_args[0][0]['subject'] == 'Template subject'
+    assert mocked_letter_template.call_args[0][0]['content'] == 'Dear Sir/Madam, Hello. Yours Truly, The Government.'
+
+    # Personalisation
+    assert mocked_letter_template.call_args[0][1] is None
+
+    # Named arguments
+    assert mocked_letter_template.call_args[1]['numeric_id'] == 999
+    assert mocked_letter_template.call_args[1]['contact_block'] == 'London,\nSW1A 1AA'
 
 
 def test_build_dvla_file_retries_if_all_notifications_are_not_created(sample_letter_template, mocker):
diff --git a/tests/app/conftest.py b/tests/app/conftest.py
index 387bb33eb..0805242b7 100644
--- a/tests/app/conftest.py
+++ b/tests/app/conftest.py
@@ -134,7 +134,8 @@ def sample_service(
         'message_limit': limit,
         'restricted': restricted,
         'email_from': email_from,
-        'created_by': user
+        'created_by': user,
+        'letter_contact_block': 'London,\nSW1A 1AA',
     }
     service = Service.query.filter_by(name=service_name).first()
     if not service: