diff --git a/apps/member/views.py b/apps/member/views.py
index 57e4b1e0..de44bfe7 100644
--- a/apps/member/views.py
+++ b/apps/member/views.py
@@ -625,9 +625,6 @@ class ClubAddMemberView(ProtectQuerysetMixin, ProtectedCreateView):
         # Retrieve form data
         credit_type = form.cleaned_data["credit_type"]
         credit_amount = form.cleaned_data["credit_amount"]
-        last_name = form.cleaned_data["last_name"]
-        first_name = form.cleaned_data["first_name"]
-        bank = form.cleaned_data["bank"]
         soge = form.cleaned_data["soge"] and not user.profile.soge and (club.name == "BDE" or club.name == "Kfet")
 
         if not credit_type:
@@ -675,16 +672,8 @@ class ClubAddMemberView(ProtectQuerysetMixin, ProtectedCreateView):
             error = True
 
         if credit_amount:
-            if not last_name or not first_name or (not bank and credit_type.special_type == "Chèque"):
-                if not last_name:
-                    form.add_error('last_name', _("This field is required."))
-                    error = True
-                if not first_name:
-                    form.add_error('first_name', _("This field is required."))
-                    error = True
-                if not bank and credit_type.special_type == "Chèque":
-                    form.add_error('bank', _("This field is required."))
-                    error = True
+            # Check that special information for payment are filled
+            error = SpecialTransaction.validate_payment_form(form) or error
 
         return not error
 
diff --git a/apps/note/models/transactions.py b/apps/note/models/transactions.py
index ac236ffe..3db82e07 100644
--- a/apps/note/models/transactions.py
+++ b/apps/note/models/transactions.py
@@ -333,6 +333,36 @@ class SpecialTransaction(Transaction):
         self.clean()
         super().save(*args, **kwargs)
 
+    @staticmethod
+    def validate_payment_form(form):
+        """
+        Ensure that last name and first name are filled for a form that creates a SpecialTransaction,
+        and check that if the user pays with a check, then the bank field is filled.
+
+        Return True iff there is no error.
+        Whenever there is an error, they are inserted in the form errors.
+        """
+
+        credit_type = form.cleaned_data["credit_type"]
+        last_name = form.cleaned_data["last_name"]
+        first_name = form.cleaned_data["first_name"]
+        bank = form.cleaned_data["bank"]
+
+        error = True
+
+        if not last_name or not first_name or (not bank and credit_type.special_type == "Chèque"):
+            if not last_name:
+                form.add_error('last_name', _("This field is required."))
+                error = True
+            if not first_name:
+                form.add_error('first_name', _("This field is required."))
+                error = True
+            if not bank and credit_type.special_type == "Chèque":
+                form.add_error('bank', _("This field is required."))
+                error = True
+
+        return not error
+
     class Meta:
         verbose_name = _("Special transaction")
         verbose_name_plural = _("Special transactions")
diff --git a/apps/registration/views.py b/apps/registration/views.py
index c0c32d15..d8238975 100644
--- a/apps/registration/views.py
+++ b/apps/registration/views.py
@@ -248,9 +248,13 @@ class FutureUserDetailView(ProtectQuerysetMixin, LoginRequiredMixin, FormMixin,
 
     @transaction.atomic
     def form_valid(self, form):
+        """
+        Finally validate the registration, with creating the membership.
+        """
         user = self.get_object()
 
         if Alias.objects.filter(normalized_name=Alias.normalize(user.username)).exists():
+            # Don't try to hack an existing account.
             form.add_error(None, _("An alias with a similar name already exists."))
             return self.form_invalid(form)
 
@@ -265,14 +269,16 @@ class FutureUserDetailView(ProtectQuerysetMixin, LoginRequiredMixin, FormMixin,
         join_kfet = form.cleaned_data["join_kfet"]
 
         if soge:
-            # If Société Générale pays the inscription, the user joins the two clubs
+            # If Société Générale pays the inscription, the user automatically joins the two clubs.
             join_bde = True
             join_kfet = True
 
         if not join_bde:
+            # This software belongs to the BDE.
             form.add_error('join_bde', _("You must join the BDE."))
             return super().form_invalid(form)
 
+        # Calculate required registration fee
         fee = 0
         bde = Club.objects.get(name="BDE")
         bde_fee = bde.membership_fee_paid if user.profile.paid else bde.membership_fee_unpaid
@@ -298,15 +304,9 @@ class FutureUserDetailView(ProtectQuerysetMixin, LoginRequiredMixin, FormMixin,
                            .format(pretty_money(fee)))
             return self.form_invalid(form)
 
-        if credit_type is not None and credit_amount > 0:
-            if not last_name or not first_name or (not bank and credit_type.special_type == "Chèque"):
-                if not last_name:
-                    form.add_error('last_name', _("This field is required."))
-                if not first_name:
-                    form.add_error('first_name', _("This field is required."))
-                if not bank and credit_type.special_type == "Chèque":
-                    form.add_error('bank', _("This field is required."))
-                return self.form_invalid(form)
+        # Check that payment information are filled, like last name and first name
+        if credit_type is not None and credit_amount > 0 and SpecialTransaction.validate_payment_form(form):
+            return self.form_invalid(form)
 
         # Save the user and finally validate the registration
         # Saving the user creates the associated note