diff --git a/billing/utils.py b/billing/utils.py
index 9693de7..57dd0fd 100644
--- a/billing/utils.py
+++ b/billing/utils.py
@@ -12,18 +12,30 @@
 #
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
+from enum import Enum, unique
 from datetime import datetime, timedelta, timezone
+
 from payments import get_payment_model, RedirectNeeded, PaymentStatus
+from django.core.mail import send_mail
+from django.urls import reverse
+from django.template.loader import render_to_string
 from django.contrib.auth.models import User
+from django.conf import settings
 from django.shortcuts import get_object_or_404
 
 from dash.models import Instance
 
+Payment = get_payment_model()
 
-def payment_fullfilled(instance: Instance) -> bool:
-    Payment = get_payment_model()
+
+def __get_delta():
     now = datetime.now(tz=timezone.utc)
     delta = now - timedelta(seconds=(60 * 60 * 24 * 30))  # one month
+    return delta
+
+
+def payment_fullfilled(instance: Instance) -> bool:
+    delta = __get_delta()
 
     payment = None
     for p in Payment.objects.filter(date__gt=(delta), instance_name=instance.name):
@@ -31,3 +43,70 @@ def payment_fullfilled(instance: Instance) -> bool:
             return True
 
     return False
+
+
+@unique
+class GenerateInvoiceErrorCode(Enum):
+    ALREADY_PAID = "already paid"
+    DUPLICATE_PAYMENT = "DUPLICATE PAYMENT"
+
+    def __str__(self) -> str:
+        return self.name
+
+
+class GenerateInvoiceException(Exception):
+    error: str
+    code: GenerateInvoiceErrorCode
+
+    def __init__(self, code: GenerateInvoiceErrorCode):
+        self.error = str(code)
+        self.code = code
+
+    def __str__(self):
+        return self.error
+
+
+def generate_invoice(instance: Instance) -> Payment:
+    delta = __get_delta()
+
+    payment = None
+    for p in Payment.objects.filter(date__gt=(delta), instance_name=instance.name):
+        if p.status == PaymentStatus.CONFIRMED:
+            raise GenerateInvoiceException(code=GenerateInvoiceErrorCode.ALREADY_PAID)
+        if any([p.status == PaymentStatus.INPUT, p.status == PaymentStatus.WAITING]):
+            if payment is None:
+                payment = p
+            else:
+                print(f"Duplicate payment {p}, deleting in favor of {payment}")
+                p.delete()
+
+    if payment is None:
+        print("Payment not found, generating new payment")
+        payment = Payment.objects.create(
+            variant="stripe",  # this is the variant from PAYMENT_VARIANTS
+            instance=instance,
+        )
+
+        invoice_link = reverse("billing.invoice.details", args=(payment.public_ref,))
+        ctx = {
+            "username": instance.owned_by.username,
+            "link": invoice_link,
+            "payment": payment,
+        }
+
+        body = render_to_string(
+            "billing/emails/payment-notification.txt",
+            context=ctx,
+        )
+
+        email = instance.owned_by.email
+        sender = settings.DEFAULT_FROM_EMAIL
+
+        send_mail(
+            subject="[Hostea] An invoice is generated for your Hostea VM",
+            message=body,
+            from_email=f"No reply Hostea<{sender}>",  # TODO read from settings.py
+            recipient_list=[email],
+        )
+
+    return payment
diff --git a/billing/views.py b/billing/views.py
index 1163518..00ac7f3 100644
--- a/billing/views.py
+++ b/billing/views.py
@@ -29,6 +29,12 @@ from dash.models import Instance
 from infrastructure.utils import create_vm_if_not_exists
 from dash.utils import footer_ctx
 
+from .utils import (
+    generate_invoice as generate_invoice_util,
+    GenerateInvoiceErrorCode,
+    GenerateInvoiceException,
+)
+
 
 def default_ctx(title: str, username: str):
     """
@@ -69,51 +75,13 @@ def paid_invoices(request):
 def generate_invoice(request, instance_name: str):
     instance = get_object_or_404(Instance, name=instance_name, owned_by=request.user)
 
-    Payment = get_payment_model()
-    now = datetime.now(tz=timezone.utc)
-    delta = now - timedelta(seconds=(60 * 60 * 24 * 30))  # one month
-
-    payment = None
-    for p in Payment.objects.filter(date__gt=(delta), instance_name=instance_name):
-        if p.status == PaymentStatus.CONFIRMED:
+    try:
+        payment = generate_invoice_util(instance=instance)
+        return redirect(reverse("billing.invoice.details", args=(payment.public_ref,)))
+    except GenerateInvoiceException as e:
+        if e.code == GenerateInvoiceErrorCode.ALREADY_PAID:
             return HttpResponse("BAD REQUEST: Already paid", status=400)
-        elif any([p.status == PaymentStatus.INPUT, p.status == PaymentStatus.WAITING]):
-            if payment is None:
-                payment = p
-            else:
-                print(f"Duplicate payment {p}, deleting in favor of {payment}")
-                p.delete()
-
-    if payment is None:
-        print("Payment not found, generating new payment")
-        payment = Payment.objects.create(
-            variant="stripe",  # this is the variant from PAYMENT_VARIANTS
-            instance=instance,
-        )
-
-        invoice_link = reverse("billing.invoice.details", args=(payment.public_ref,))
-        ctx = {
-            "username": request.user.username,
-            "link": invoice_link,
-            "payment": payment,
-        }
-
-        body = render_to_string(
-            "billing/emails/payment-notification.txt",
-            context=ctx,
-        )
-
-        email = request.user.email
-        sender = settings.DEFAULT_FROM_EMAIL
-
-        send_mail(
-            subject="[Hostea] An invoice is generated for your Hostea VM",
-            message=body,
-            from_email=f"No reply Hostea<{sender}>",  # TODO read from settings.py
-            recipient_list=[email],
-        )
-
-        return redirect(invoice_link)
+        return redirect(reverse("dash.home"))
 
 
 @login_required