diff --git a/app/main/views/uploads.py b/app/main/views/uploads.py
index 5166d1ed8..263fd43bf 100644
--- a/app/main/views/uploads.py
+++ b/app/main/views/uploads.py
@@ -115,7 +115,12 @@ def upload_letter(service_id):
         file_location = get_transient_letter_file_location(service_id, upload_id)
 
         try:
-            response = sanitise_letter(BytesIO(pdf_file_bytes))
+            response = sanitise_letter(
+                BytesIO(pdf_file_bytes),
+                allow_international_letters=current_service.has_permission(
+                    'international_letters'
+                ),
+            )
             response.raise_for_status()
         except RequestException as ex:
             if ex.response is not None and ex.response.status_code == 400:
diff --git a/app/template_previews.py b/app/template_previews.py
index 7bf488cc5..1a1353e89 100644
--- a/app/template_previews.py
+++ b/app/template_previews.py
@@ -94,9 +94,12 @@ def get_page_count_for_letter(template, values=None):
     return page_count
 
 
-def sanitise_letter(pdf_file):
+def sanitise_letter(pdf_file, *, allow_international_letters):
     return requests.post(
-        '{}/precompiled/sanitise'.format(current_app.config['TEMPLATE_PREVIEW_API_HOST']),
+        '{}/precompiled/sanitise?allow_international_letters={}'.format(
+            current_app.config['TEMPLATE_PREVIEW_API_HOST'],
+            'true' if allow_international_letters else 'false',
+        ),
         data=pdf_file,
         headers={'Authorization': 'Token {}'.format(current_app.config['TEMPLATE_PREVIEW_API_KEY'])}
     )
diff --git a/tests/app/main/views/test_uploads.py b/tests/app/main/views/test_uploads.py
index 1c0d6b248..98246762a 100644
--- a/tests/app/main/views/test_uploads.py
+++ b/tests/app/main/views/test_uploads.py
@@ -143,16 +143,22 @@ def test_get_upload_letter(client_request):
     assert normalize_spaces(page.find('label', class_='file-upload-button').text) == 'Choose file'
 
 
+@pytest.mark.parametrize('extra_permissions, expected_allow_international', (
+    ([], False),
+    (['international_letters'], True),
+))
 def test_post_upload_letter_redirects_for_valid_file(
     mocker,
     active_user_with_permissions,
     service_one,
     client_request,
     fake_uuid,
+    extra_permissions,
+    expected_allow_international,
 ):
     mocker.patch('uuid.uuid4', return_value=fake_uuid)
     antivirus_mock = mocker.patch('app.main.views.uploads.antivirus_client.scan', return_value=True)
-    mocker.patch(
+    mock_sanitise = mocker.patch(
         'app.main.views.uploads.sanitise_letter',
         return_value=Mock(
             content='The sanitised content',
@@ -169,6 +175,7 @@ def test_post_upload_letter_redirects_for_valid_file(
     mocker.patch('app.main.views.uploads.service_api_client.get_precompiled_template')
 
     service_one['restricted'] = False
+    service_one['permissions'] += extra_permissions
     client_request.login(active_user_with_permissions, service=service_one)
 
     with open('tests/test_pdf_files/one_page_pdf.pdf', 'rb') as file:
@@ -188,6 +195,10 @@ def test_post_upload_letter_redirects_for_valid_file(
         filename='tests/test_pdf_files/one_page_pdf.pdf',
         recipient='The Queen',
     )
+    mock_sanitise.assert_called_once_with(
+        ANY,
+        allow_international_letters=expected_allow_international,
+    )
 
     assert 'The Queen' in page.find('div', class_='js-stick-at-bottom-when-scrolling').text
     assert page.find('h1').text == 'tests/test_pdf_files/one_page_pdf.pdf'
diff --git a/tests/app/test_template_previews.py b/tests/app/test_template_previews.py
index 4fdd73bbf..1f205412b 100644
--- a/tests/app/test_template_previews.py
+++ b/tests/app/test_template_previews.py
@@ -164,13 +164,21 @@ def test_from_example_template_makes_request(mocker):
     )
 
 
-def test_sanitise_letter_calls_template_preview_sanitise_endoint_with_file(mocker):
+@pytest.mark.parametrize('allow_international_letters, expected_url', (
+    (False, 'http://localhost:9999/precompiled/sanitise?allow_international_letters=false'),
+    (True, 'http://localhost:9999/precompiled/sanitise?allow_international_letters=true'),
+))
+def test_sanitise_letter_calls_template_preview_sanitise_endoint_with_file(
+    mocker,
+    allow_international_letters,
+    expected_url,
+):
     request_mock = mocker.patch('app.template_previews.requests.post')
 
-    sanitise_letter('pdf_data')
+    sanitise_letter('pdf_data', allow_international_letters=allow_international_letters)
 
     request_mock.assert_called_once_with(
-        'http://localhost:9999/precompiled/sanitise',
+        expected_url,
         headers={'Authorization': 'Token my-secret-key'},
         data='pdf_data'
     )