diff --git a/addons/crm/base_partner_merge.py b/addons/crm/base_partner_merge.py
index c07a32579f0..11cacc57ce6 100644
--- a/addons/crm/base_partner_merge.py
+++ b/addons/crm/base_partner_merge.py
@@ -378,11 +378,20 @@ class MergePartnerAutomatic(osv.TransientModel):
         return {'type': 'ir.actions.act_window_close'}
 
     def _generate_query(self, fields, maximum_group=100):
-        group_fields = ', '.join(fields)
+        sql_fields = []
+        for field in fields:
+            if field in ['email', 'name']:
+                sql_fields.append('lower(%s)' % field)
+            elif field in ['vat']:
+                sql_fields.append("replace(%s, ' ', '')" % field)
+            else:
+                sql_fields.append(field)
+
+        group_fields = ', '.join(sql_fields)
 
         filters = []
         for field in fields:
-            if field in ['email', 'name']:
+            if field in ['email', 'name', 'vat']:
                 filters.append((field, 'IS NOT', 'NULL'))
 
         criteria = ' AND '.join('%s %s %s' % (field, operator, value)