diff --git a/src/pretix/base/forms/questions.py b/src/pretix/base/forms/questions.py
index 1fd4b8759..ca29fd10a 100644
--- a/src/pretix/base/forms/questions.py
+++ b/src/pretix/base/forms/questions.py
@@ -1415,6 +1415,7 @@ class BaseInvoiceAddressForm(forms.ModelForm):
                     if not data.get(r):
                         raise ValidationError({r: _("This field is required for the selected type of invoice transmission.")})
 
+                transmission_type.validate_invoice_address_data(data)
                 self.instance.transmission_type = transmission_type.identifier
                 self.instance.transmission_info = transmission_type.form_data_to_transmission_info(data)
             elif transmission_type.is_exclusive(self.event, data.get("country"), data.get("is_business")):
diff --git a/src/pretix/base/invoicing/peppol.py b/src/pretix/base/invoicing/peppol.py
index 194bf195e..0a26b6c10 100644
--- a/src/pretix/base/invoicing/peppol.py
+++ b/src/pretix/base/invoicing/peppol.py
@@ -204,6 +204,12 @@ class PeppolTransmissionType(TransmissionType):
         }
         return base | {"transmission_peppol_participant_id"}
 
+    def validate_invoice_address_data(self, address_data: dict):
+        # Special case Belgium: If a Belgian business ID is used as Peppol ID, it should match the VAT ID
+        if address_data.get("transmission_peppol_participant_id").startswith("0208:") and address_data.get("vat_id"):
+            if address_data["vat_id"].removeprefix("BE") != address_data["transmission_peppol_participant_id"].removeprefix("0208:"):
+                raise ValidationError({"transmission_peppol_participant_id": _("The Peppol participant ID does not match your VAT ID.")})
+
     def pdf_watermark(self) -> str:
         return pgettext("peppol_invoice", "Visual copy")
 
diff --git a/src/pretix/base/invoicing/transmission.py b/src/pretix/base/invoicing/transmission.py
index 9c6899381..a82bef73b 100644
--- a/src/pretix/base/invoicing/transmission.py
+++ b/src/pretix/base/invoicing/transmission.py
@@ -24,7 +24,7 @@ from typing import Optional
 from django.utils.translation import gettext_lazy as _
 from django_countries.fields import Country
 
-from pretix.base.models import Invoice, InvoiceAddress
+from pretix.base.models import Invoice
 from pretix.base.signals import EventPluginRegistry, Registry
 
 
@@ -89,7 +89,7 @@ class TransmissionType:
     def invoice_address_form_fields_visible(self, country: Country, is_business: bool) -> set:
         return set(self.invoice_address_form_fields.keys())
 
-    def validate_address(self, ia: InvoiceAddress):
+    def validate_invoice_address_data(self, address_data: dict):
         pass
 
     @property