Require payment even if total consists only of fees

src/pretix/base/payment.py

@@ -591,7 +591,11 @@ class FreeOrderProvider(BasePaymentProvider):
         messages.success(request, _('The order has been marked as refunded.'))
 
     def is_allowed(self, request: HttpRequest) -> bool:
-        return get_cart_total(request) == 0
+        from .services.cart import get_fees
+
+        total = get_cart_total(request)
+        total += sum([f.value for f in get_fees(self.event, request, total, None, None)])
+        return total == 0
 
     def order_change_allowed(self, order: Order) -> bool:
         return False

src/pretix/base/services/cart.py

@@ -631,10 +631,7 @@ def update_tax_rates(event: Event, cart_id: str, invoice_address: InvoiceAddress
 def get_fees(event, request, total, invoice_address, provider):
     fees = []
 
-    if total == 0:
-        return fees
-
-    if provider:
+    if provider and total != 0:
         provider = event.get_payment_providers().get(provider)
         if provider:
             payment_fee = provider.calculate_fee(total)