diff --git a/passerelle/contrib/solis_afi_mss/models.py b/passerelle/contrib/solis_afi_mss/models.py
index 7c7a5010..cafeda8d 100644
--- a/passerelle/contrib/solis_afi_mss/models.py
+++ b/passerelle/contrib/solis_afi_mss/models.py
@@ -66,6 +66,11 @@ TAX_SCHEMA = {
             'description': 'Tax amount',
             'type': 'string',
         },
+        'indexIndividus': {
+            'description': "List of related family member indexes separated by ':'",
+            'type': 'string',
+            'pattern': r'^[0-9 :]+$',
+        },
     },
 }
 
@@ -332,7 +337,15 @@ class SolisAfiMss(BaseResource, HTTPResource):
         post={'request_body': {'schema': {'application/json': TAX_SCHEMA}}},
     )
     def declare_tax(self, request, email, post_data):
-        post_data['indexAgent'] = str(self.search_from_email(email)['index'])
+        results = self.search_from_email(email)
+        post_data['indexAgent'] = str(results['index'])
+        if post_data.get('indexIndividus'):
+            related_persons = []
+            for person in results['adults'] + results['children']:
+                for index in [x.strip() for x in post_data['indexIndividus'].split(':') if x.strip()]:
+                    if str(person['indexIndividu']) == index:
+                        related_persons.append(index)
+            post_data['indexIndividus'] = related_persons
         response = self.request(self.base_url + 'afi/budget/declarerImpot/', json=post_data)
         return {'data': response}
 
diff --git a/tests/test_solis_afi_mss.py b/tests/test_solis_afi_mss.py
index a7c0354e..fccc7e0a 100644
--- a/tests/test_solis_afi_mss.py
+++ b/tests/test_solis_afi_mss.py
@@ -523,6 +523,30 @@ def test_declare_tax(mocked_post, mocked_get, app, connector, response1, respons
     data.pop('err_desc')
     assert resp.json == {'err': 0, 'data': data}
 
+    mocked_post.reset_mock()
+    mocked_get.side_effect = [response1]
+    mocked_post.side_effect = [response2]
+    payload['indexIndividus'] = '434729:389229 :389230:  ::424242:'
+    resp = app.post_json(endpoint + '?email=foo@dummy.org', params=payload)
+    assert mocked_post.mock_calls == [
+        mock.call(
+            'https://solis-afi-mss.example.net/afi/budget/declarerImpot/',
+            headers={'Accept': 'application/json'},
+            json={
+                'indexAgent': '389227',
+                'indexImposition': '368',
+                'anneeImposition': '2011',
+                'nombrePartImposition': '3.2',
+                'montantImposition': '777.77',
+                'indexIndividus': ['434729', '389229', '389230'],
+            },
+        )
+    ]
+    data = json.loads(response2.content)
+    data.pop('err')
+    data.pop('err_desc')
+    assert resp.json == {'err': 0, 'data': data}
+
 
 @mock.patch('passerelle.utils.Request.get')
 @mock.patch('passerelle.utils.Request.post')