diff --git a/uncloud_django_based/uncloud/uncloud_pay/migrations/0003_auto_20200305_1354.py b/uncloud_django_based/uncloud/uncloud_pay/migrations/0003_auto_20200305_1354.py
new file mode 100644
index 0000000..d99ece7
--- /dev/null
+++ b/uncloud_django_based/uncloud/uncloud_pay/migrations/0003_auto_20200305_1354.py
@@ -0,0 +1,18 @@
+# Generated by Django 3.0.3 on 2020-03-05 13:54
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('uncloud_pay', '0002_auto_20200305_1524.py'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='paymentmethod',
+            name='primary',
+            field=models.BooleanField(default=False, editable=False),
+        ),
+    ]
diff --git a/uncloud_django_based/uncloud/uncloud_pay/models.py b/uncloud_django_based/uncloud/uncloud_pay/models.py
index 10ae985..f7aee62 100644
--- a/uncloud_django_based/uncloud/uncloud_pay/models.py
+++ b/uncloud_django_based/uncloud/uncloud_pay/models.py
@@ -4,9 +4,7 @@ from django.contrib.auth import get_user_model
 from django.core.validators import MinValueValidator
 from django.utils.translation import gettext_lazy as _
 from django.utils import timezone
-from django.dispatch import receiver
 from django.core.exceptions import ObjectDoesNotExist
-import django.db.models.signals as signals
 
 import uuid
 from functools import reduce
@@ -106,7 +104,7 @@ class PaymentMethod(models.Model):
                 ),
             default='stripe')
     description = models.TextField()
-    primary = models.BooleanField(default=True)
+    primary = models.BooleanField(default=False, editable=False)
 
     # Only used for "Stripe" source
     stripe_payment_method_id = models.CharField(max_length=32, blank=True, null=True)
@@ -149,22 +147,24 @@ class PaymentMethod(models.Model):
         else:
             raise Exception('This payment method is unsupported/cannot be charged.')
 
+    def set_as_primary_for(self, user):
+        methods = PaymentMethod.objects.filter(owner=user, primary=True)
+        for method in methods:
+            print(method)
+            method.primary = False
+            method.save()
+
+        self.primary = True
+        self.save()
 
     def get_primary_for(user):
         methods = PaymentMethod.objects.filter(owner=user)
         for method in methods:
-            # Do we want to do something with non-primary method?
-            if method.active and method.primary:
+            if method.primary:
                 return method
 
         return None
 
-    class Meta:
-        # TODO: limit to one primary method per user.
-        # unique_together is no good since it won't allow more than one
-        # non-primary method.
-        pass
-
 ###
 # Bills.
 
diff --git a/uncloud_django_based/uncloud/uncloud_pay/serializers.py b/uncloud_django_based/uncloud/uncloud_pay/serializers.py
index f408d1b..72316a6 100644
--- a/uncloud_django_based/uncloud/uncloud_pay/serializers.py
+++ b/uncloud_django_based/uncloud/uncloud_pay/serializers.py
@@ -20,7 +20,7 @@ class PaymentMethodSerializer(serializers.ModelSerializer):
 class UpdatePaymentMethodSerializer(serializers.ModelSerializer):
     class Meta:
         model = PaymentMethod
-        fields = ['description', 'primary']
+        fields = ['description']
 
 class ChargePaymentMethodSerializer(serializers.Serializer):
     amount = serializers.DecimalField(max_digits=10, decimal_places=2)
@@ -29,7 +29,8 @@ class CreatePaymentMethodSerializer(serializers.ModelSerializer):
     please_visit = serializers.CharField(read_only=True)
     class Meta:
         model = PaymentMethod
-        fields = ['source', 'description', 'primary', 'please_visit']
+        fields = ['uuid', 'primary', 'source', 'description', 'please_visit']
+        read_only_field = ['uuid', 'primary']
 
 ###
 # Orders & Products.
diff --git a/uncloud_django_based/uncloud/uncloud_pay/views.py b/uncloud_django_based/uncloud/uncloud_pay/views.py
index 567874d..762a3c0 100644
--- a/uncloud_django_based/uncloud/uncloud_pay/views.py
+++ b/uncloud_django_based/uncloud/uncloud_pay/views.py
@@ -64,6 +64,10 @@ class PaymentMethodViewSet(viewsets.ModelViewSet):
         serializer = self.get_serializer(data=request.data)
         serializer.is_valid(raise_exception=True)
 
+        # Set newly created method as primary if no other method is.
+        if PaymentMethod.get_primary_for(request.user) == None:
+            serializer.validated_data['primary'] = True
+
         if serializer.validated_data['source'] == "stripe":
             # Retrieve Stripe customer ID for user.
             customer_id = uncloud_stripe.get_customer_id_for(request.user)
@@ -109,6 +113,7 @@ class PaymentMethodViewSet(viewsets.ModelViewSet):
     @action(detail=True, methods=['get'], url_path='register-stripe-cc', renderer_classes=[TemplateHTMLRenderer])
     def register_stripe_cc(self, request, pk=None):
         payment_method = self.get_object()
+
         if payment_method.source != 'stripe':
             return Response(
                     {'error': 'This is not a Stripe-based payment method.'},
@@ -163,6 +168,14 @@ class PaymentMethodViewSet(viewsets.ModelViewSet):
             error = 'Could not fetch payment method from stripe. Please try again.'
             return Response({'error': error})
 
+    @action(detail=True, methods=['post'], url_path='set-as-primary')
+    def set_as_primary(self, request, pk=None):
+        payment_method = self.get_object()
+        payment_method.set_as_primary_for(request.user)
+
+        serializer = self.get_serializer(payment_method)
+        return Response(serializer.data)
+
 ###
 # Bills and Orders.