diff --git a/cotisations/migrations/0030_custom_payment.py b/cotisations/migrations/0030_custom_payment.py
index bdd7cde9..785cc06c 100644
--- a/cotisations/migrations/0030_custom_payment.py
+++ b/cotisations/migrations/0030_custom_payment.py
@@ -103,6 +103,7 @@ class Migration(migrations.Migration):
                 ('payment_credential', models.CharField(blank=True, default='', max_length=255, verbose_name='ComNpay VAD Number')),
                 ('payment_pass', re2o.aes_field.AESEncryptedField(blank=True, max_length=255, null=True, verbose_name='ComNpay Secret Key')),
                 ('payment', models.OneToOneField(editable=False, on_delete=django.db.models.deletion.CASCADE, related_name='payment_method', to='cotisations.Paiement')),
+                ('minimum_payment', models.DecimalField(decimal_places=2, default=1, help_text='The minimal amount of money you have to use when paying with ComNpay', max_digits=5, verbose_name='Minimum payment')),
             ],
             bases=(cotisations.payment_methods.mixins.PaymentMethodMixin, models.Model),
         ),
diff --git a/cotisations/models.py b/cotisations/models.py
index 923b0b98..8b6d5a8c 100644
--- a/cotisations/models.py
+++ b/cotisations/models.py
@@ -155,7 +155,7 @@ class Facture(RevMixin, AclMixin, FieldPermissionModelMixin, models.Model):
                 models.F('prix')*models.F('number'),
                 output_field=models.FloatField()
             )
-        )['total']
+        )['total'] or 0
 
     def name(self):
         """
diff --git a/cotisations/payment_methods/balance/models.py b/cotisations/payment_methods/balance/models.py
index 958906fa..b4ae7e40 100644
--- a/cotisations/payment_methods/balance/models.py
+++ b/cotisations/payment_methods/balance/models.py
@@ -95,3 +95,24 @@ class BalancePayment(PaymentMethodMixin, models.Model):
     def alter_payment(self, payment):
         """Register the payment as a balance payment."""
         self.payment.is_balance = True
+
+    def check_invoice(self, invoice_form):
+        """Checks that a invoice meets the requirement to be paid with user
+        balance.
+
+        Args:
+            invoice_form: The invoice_form which is to be checked.
+
+        Returns:
+            True if the form is valid for this payment.
+
+        """
+        user = invoice_form.instance.user
+        total_price = invoice_form.instance.prix_total()
+        if float(user.solde) - float(total_price) < self.minimum_balance:
+            invoice_form.add_error(
+                'paiement',
+                _("Your balance is too low for this operation.")
+            )
+            return False
+        return True
diff --git a/cotisations/payment_methods/comnpay/models.py b/cotisations/payment_methods/comnpay/models.py
index d32e0a06..4dfe62de 100644
--- a/cotisations/payment_methods/comnpay/models.py
+++ b/cotisations/payment_methods/comnpay/models.py
@@ -53,6 +53,14 @@ class ComnpayPayment(PaymentMethodMixin, models.Model):
         blank=True,
         verbose_name=_l("ComNpay Secret Key"),
     )
+    minimum_payment = models.DecimalField(
+        verbose_name=_l("Minimum payment"),
+        help_text=_l("The minimal amount of money you have to use when paying"
+                     " with ComNpay"),
+        max_digits=5,
+        decimal_places=2,
+        default=1,
+    )
 
     def end_payment(self, invoice, request):
         """
@@ -86,3 +94,23 @@ class ComnpayPayment(PaymentMethodMixin, models.Model):
             'amount': invoice.prix_total(),
         }
         return render(request, 'cotisations/payment.html', r)
+
+    def check_invoice(self, invoice_form):
+        """Checks that a invoice meets the requirement to be paid with ComNpay.
+
+        Args:
+            invoice_form: The invoice_form which is to be checked.
+
+        Returns:
+            True if the form is valid for ComNpay.
+
+        """
+        if invoice_form.instance.prix_total() < self.minimum_payment:
+            invoice_form.add_error(
+                'paiement',
+                _('In order to pay your invoice with ComNpay'
+                  ', the price must be grater than {} €')
+                .format(self.minimum_payment)
+            )
+            return False
+        return True
diff --git a/cotisations/views.py b/cotisations/views.py
index f561147b..2d7de6c6 100644
--- a/cotisations/views.py
+++ b/cotisations/views.py
@@ -74,6 +74,7 @@ from .forms import (
 )
 from .tex import render_invoice
 from .payment_methods.forms import payment_method_factory
+from cotisations.utils import find_payment_method
 
 
 @login_required
@@ -118,8 +119,8 @@ def new_facture(request, user, userid):
         # Check if at leat one article has been selected
         if any(art.cleaned_data for art in articles):
             new_invoice_instance.save()
-
             # Building a purchase for each article sold
+            purchases = []
             for art_item in articles:
                 if art_item.cleaned_data:
                     article = art_item.cleaned_data['article']
@@ -132,17 +133,24 @@ def new_facture(request, user, userid):
                         duration=article.duration,
                         number=quantity
                     )
-                    new_purchase.save()
-
-            return new_invoice_instance.paiement.end_payment(
-                new_invoice_instance,
-                request
+                    purchases.append(new_purchase)
+            p = find_payment_method(new_invoice_instance.paiement)
+            if hasattr(p, 'check_invoice'):
+                accept = p.check_invoice(invoice_form)
+            else:
+                accept = True
+            if accept:
+                return new_invoice_instance.paiement.end_payment(
+                    new_invoice_instance,
+                    request
+                )
+            else:
+                new_invoice_instance.delete()
+        else:
+            messages.error(
+                request,
+                _("You need to choose at least one article.")
             )
-
-        messages.error(
-            request,
-            _("You need to choose at least one article.")
-        )
     p = Paiement.objects.filter(is_balance=True)
     if len(p) and p[0].can_use_payment(request.user):
         balance = user.solde