diff --git a/zilencer/lib/stripe.py b/zilencer/lib/stripe.py
index b6783ace26..f7c175cde0 100644
--- a/zilencer/lib/stripe.py
+++ b/zilencer/lib/stripe.py
@@ -9,6 +9,7 @@ from django.conf import settings
 from django.db import transaction
 from django.utils.translation import ugettext as _
 from django.core.signing import Signer
+from django.core import signing
 import stripe
 
 from zerver.lib.exceptions import JsonableError
@@ -177,3 +178,27 @@ def do_subscribe_customer_to_plan(stripe_customer: stripe.Customer, stripe_plan_
                 event_time=timestamp_to_datetime(stripe_subscription.created),
                 requires_billing_update=True,
                 extra_data=ujson.dumps({'quantity': current_seat_count}))
+
+def process_initial_upgrade(user: UserProfile, plan: str, signed_seat_count: str,
+                            salt: str, stripe_token: str) -> Optional[str]:
+    if plan not in [Plan.CLOUD_ANNUAL, Plan.CLOUD_MONTHLY]:
+        billing_logger.warning("Tampered plan during realm upgrade. user: %s, realm: %s (%s)."
+                               % (user.id, user.realm.id, user.realm.string_id))
+        return "Something went wrong. Please contact support@zulipchat.com"
+    try:
+        seat_count = int(unsign_string(signed_seat_count, salt))
+    except signing.BadSignature:
+        billing_logger.warning("Tampered seat count during realm upgrade. user: %s, realm: %s (%s)."
+                               % (user.id, user.realm.id, user.realm.string_id))
+        return "Something went wrong. Please contact support@zulipchat.com"
+
+    stripe_customer = do_create_customer_with_payment_source(user, stripe_token)
+    do_subscribe_customer_to_plan(
+        stripe_customer=stripe_customer,
+        stripe_plan_id=Plan.objects.get(nickname=plan).stripe_plan_id,
+        seat_count=seat_count,
+        # TODO: billing address details are passed to us in the request;
+        # use that to calculate taxes.
+        tax_percent=0)
+    # TODO: check for errors and raise/send to frontend
+    return None
diff --git a/zilencer/views.py b/zilencer/views.py
index 435d5b225c..93137dcacc 100644
--- a/zilencer/views.py
+++ b/zilencer/views.py
@@ -3,7 +3,6 @@ import logging
 
 from django.core.exceptions import ValidationError
 from django.core.validators import validate_email, URLValidator
-from django.core import signing
 from django.db import IntegrityError
 from django.http import HttpRequest, HttpResponse, HttpResponseRedirect
 from django.utils import timezone
@@ -26,9 +25,8 @@ from zerver.lib.timestamp import timestamp_to_datetime
 from zerver.models import UserProfile, Realm
 from zerver.views.push_notifications import validate_token
 from zilencer.lib.stripe import STRIPE_PUBLISHABLE_KEY, StripeError, \
-    do_create_customer_with_payment_source, do_subscribe_customer_to_plan, \
     get_stripe_customer, get_upcoming_invoice, get_seat_count, \
-    extract_current_subscription, sign_string, unsign_string
+    extract_current_subscription, process_initial_upgrade, sign_string
 from zilencer.models import RemotePushDeviceToken, RemoteZulipServer, \
     Customer, Plan
 
@@ -171,28 +169,10 @@ def initial_upgrade(request: HttpRequest) -> HttpResponse:
         return HttpResponseRedirect(reverse('zilencer.views.billing_home'))
 
     if request.method == 'POST':
-        plan = request.POST['plan']
-        if plan not in [Plan.CLOUD_ANNUAL, Plan.CLOUD_MONTHLY]:
-            billing_logger.warning("Tampered plan during realm upgrade. user: %s, realm: %s (%s)."
-                                   % (user.id, user.realm.id, user.realm.string_id))
-            error_message = "Something went wrong. Please contact support@zulipchat.com"
-        try:
-            seat_count = int(unsign_string(request.POST['signed_seat_count'], request.POST['salt']))
-        except signing.BadSignature:
-            billing_logger.warning("Tampered seat count during realm upgrade. user: %s, realm: %s (%s)."
-                                   % (user.id, user.realm.id, user.realm.string_id))
-            error_message = "Something went wrong. Please contact support@zulipchat.com"
-
+        error_message = process_initial_upgrade(user, request.POST['plan'],
+                                                request.POST['signed_seat_count'],
+                                                request.POST['salt'], request.POST['stripeToken']) or ""
         if not error_message:
-            stripe_customer = do_create_customer_with_payment_source(user, request.POST['stripeToken'])
-            do_subscribe_customer_to_plan(
-                stripe_customer=stripe_customer,
-                stripe_plan_id=Plan.objects.get(nickname=plan).stripe_plan_id,
-                seat_count=seat_count,
-                # TODO: billing address details are passed to us in the request;
-                # use that to calculate taxes.
-                tax_percent=0)
-            # TODO: check for errors and raise/send to frontend
             return HttpResponseRedirect(reverse('zilencer.views.billing_home'))
 
     seat_count = get_seat_count(user.realm)