diff --git a/addons/l10n_dk_oioubl/models/account_edi_xml_oioubl_201.py b/addons/l10n_dk_oioubl/models/account_edi_xml_oioubl_201.py
index 5f72508b57e..60571916ce9 100644
--- a/addons/l10n_dk_oioubl/models/account_edi_xml_oioubl_201.py
+++ b/addons/l10n_dk_oioubl/models/account_edi_xml_oioubl_201.py
@@ -32,7 +32,7 @@ TAX_POSSIBLE_VALUES = set(UBL_TO_OIOUBL_TAX_CATEGORY_ID_MAPPING.values())
 
 
 def format_vat_number(partner):
-    vat = partner.vat.replace(' ', '')
+    vat = (partner.vat or '').replace(' ', '')
     if vat[:2].isnumeric():
         vat = partner.country_code.upper() + vat
     return vat
@@ -275,6 +275,7 @@ class AccountEdiXmlOIOUBL201(models.AbstractModel):
             if partner.country_code == "FR" and not partner.company_registry:
                 constraints["oioubl201_company_registry_required_for_french_partner"] = \
                         _("The company registry is required for french partner: %s", partner.name)
+            constraints[f'oioubl201_{partner_type}_vat_required'] = self._check_required_fields(vals[partner_type], 'vat')
 
         return constraints
 
diff --git a/addons/l10n_dk_oioubl/tests/test_xml_oioubl_dk.py b/addons/l10n_dk_oioubl/tests/test_xml_oioubl_dk.py
index 7c1b8689d87..a83fef9d70a 100644
--- a/addons/l10n_dk_oioubl/tests/test_xml_oioubl_dk.py
+++ b/addons/l10n_dk_oioubl/tests/test_xml_oioubl_dk.py
@@ -103,7 +103,10 @@ class TestUBLDK(TestUBLCommon, TestAccountMoveSendCommon):
             ],
         })
         invoice.action_post()
-        invoice._generate_pdf_and_send_invoice(self.move_template, allow_fallback_pdf=False)
+        self.env['account.move.send'] \
+            .with_context(active_model=invoice._name, active_ids=invoice.ids) \
+            .create({}) \
+            .action_send_and_print()
         return invoice
 
     #########
@@ -173,6 +176,17 @@ class TestUBLDK(TestUBLCommon, TestAccountMoveSendCommon):
         with self.assertRaisesRegex(UserError, "The company registry is required for french partner:"):
             self.create_post_and_send_invoice(partner=self.partner_c)
 
+    @freeze_time('2017-01-01')
+    def test_oioubl_export_partner_without_vat_number(self):
+        """ This test verifies that we can't export an OIOUBL file for a partner
+            who doesn't have a tax ID. It verifies that we receive a UserError
+            telling to the user that this field is missing.
+        """
+        self.partner_b.vat = None
+        with self.assertRaises(UserError) as exception:
+            self.create_post_and_send_invoice(partner=self.partner_b)
+        self.assertIn(f"The field '{self.partner_b._fields['vat'].string}' is required", exception.exception.args[0])
+
     #########
     # IMPORT
     #########