diff --git a/addons/base_vat/models/res_partner.py b/addons/base_vat/models/res_partner.py
index af0f09ac077..c6dc7d5cd19 100644
--- a/addons/base_vat/models/res_partner.py
+++ b/addons/base_vat/models/res_partner.py
@@ -69,7 +69,12 @@ _ref_vat = {
     'si': 'SI12345679',
     'sk': 'SK2022749619',
     'sm': 'SM24165',
-    'tr': 'TR1234567890 (VERGINO) or TR17291716060 (TCKIMLIKNO)'  # Levent Karakas @ Eska Yazilim A.S.
+    'tr': 'TR1234567890 (VERGINO) or TR17291716060 (TCKIMLIKNO)',  # Levent Karakas @ Eska Yazilim A.S.
+    'xi': 'XI123456782',
+}
+
+_region_specific_vat_codes = {
+    'xi',
 }
 
 
@@ -179,8 +184,10 @@ class ResPartner(models.Model):
 
         # First check with country code as prefix of the TIN
         vat_country_code, vat_number_split = self._split_vat(vat_number)
-        vat_guessed_country = self.env['res.country'].search([('code', '=', vat_country_code.upper())])
-        if vat_guessed_country:
+        vat_has_legit_country_code = self.env['res.country'].search([('code', '=', vat_country_code.upper())])
+        if not vat_has_legit_country_code:
+            vat_has_legit_country_code = vat_country_code.lower() in _region_specific_vat_codes
+        if vat_has_legit_country_code:
             check_result = check_func(vat_country_code, vat_number_split)
             if check_result:
                 return vat_country_code