diff --git a/cart/templates/cart.html b/cart/templates/cart.html
index cae3dd4a..26be9365 100644
--- a/cart/templates/cart.html
+++ b/cart/templates/cart.html
@@ -42,7 +42,7 @@
             <tfoot>
                 <tr>
                     <td colspan="4">
-                        <a href="{% url 'checkout_interstitial_page' %}" class="btn btn-primary float-end">Check Out</a>
+                        <a href="{% url 'checkout_interstitial_page' system_slug=basket.integrated_system.slug %}" class="btn btn-primary float-end">Check Out</a>
                     </td>
                 </tr>
             </tfoot>
diff --git a/cart/urls.py b/cart/urls.py
index 88aa1da5..f4728195 100644
--- a/cart/urls.py
+++ b/cart/urls.py
@@ -6,9 +6,9 @@
 
 urlpatterns = [
     path(
-        "checkout/to_payment",
+        "checkout/to_payment/<str:system_slug>/",
         CheckoutInterstitialView.as_view(),
         name="checkout_interstitial_page",
     ),
-    path("", CartView.as_view(), name="cart"),
+    path("cart/<str:system_slug>/", CartView.as_view(), name="cart"),
 ]
diff --git a/cart/views.py b/cart/views.py
index c0c6e719..b25daff1 100644
--- a/cart/views.py
+++ b/cart/views.py
@@ -12,7 +12,7 @@
 
 from payments import api
 from payments.models import Basket
-from system_meta.models import Product
+from system_meta.models import IntegratedSystem, Product
 
 log = logging.getLogger(__name__)
 
@@ -23,9 +23,10 @@ class CartView(LoginRequiredMixin, TemplateView):
     template_name = "cart.html"
     extra_context = {"title": "Cart", "innertitle": "Cart"}
 
-    def get(self, request: HttpRequest) -> HttpResponse:
+    def get(self, request: HttpRequest, system_slug: str) -> HttpResponse:
         """Render the cart page."""
-        basket = Basket.establish_basket(request)
+        system = IntegratedSystem.objects.get(slug=system_slug)
+        basket = Basket.establish_basket(request, system)
         products = Product.objects.all()
 
         if not request.user.is_authenticated:
@@ -57,10 +58,11 @@ class CheckoutInterstitialView(LoginRequiredMixin, TemplateView):
 
     template_name = "checkout_interstitial.html"
 
-    def get(self, request):
+    def get(self, request, system_slug):
         """Render the checkout interstitial page."""
         try:
-            checkout_payload = api.generate_checkout_payload(request)
+            system = IntegratedSystem.objects.get(slug=system_slug)
+            checkout_payload = api.generate_checkout_payload(request, system)
         except ObjectDoesNotExist:
             return HttpResponse("No basket")
         if (
diff --git a/payments/api.py b/payments/api.py
index a7f84161..06efdafb 100644
--- a/payments/api.py
+++ b/payments/api.py
@@ -35,9 +35,9 @@
 log = logging.getLogger(__name__)
 
 
-def generate_checkout_payload(request):
+def generate_checkout_payload(request, system):
     """Generate the payload to send to the payment gateway."""
-    basket = Basket.establish_basket(request)
+    basket = Basket.establish_basket(request, system)
 
     # Notes for future implementation: this used to check for
     # * Blocked products (by country)
diff --git a/payments/api_test.py b/payments/api_test.py
index 3ecfa8e0..f8c0b72f 100644
--- a/payments/api_test.py
+++ b/payments/api_test.py
@@ -146,7 +146,8 @@ def create_basket(user, products):
     Bootstrap a basket with a product in it for testing the discount
     redemption APIs
     """
-    basket = Basket(user=user)
+    integrated_system = products[0].system
+    basket = Basket(user=user, integrated_system=integrated_system)
     basket.save()
 
     basket_item = BasketItem(
@@ -414,7 +415,7 @@ def test_process_cybersource_payment_response(rf, mocker, user, products):
         return_value=True,
     )
     create_basket(user, products)
-    resp = generate_checkout_payload(generate_mocked_request(user))
+    resp = generate_checkout_payload(generate_mocked_request(user), products[0].system)
 
     payload = resp["payload"]
     payload = {
@@ -453,7 +454,7 @@ def test_process_cybersource_payment_decline_response(
     )
     create_basket(user, products)
 
-    resp = generate_checkout_payload(generate_mocked_request(user))
+    resp = generate_checkout_payload(generate_mocked_request(user), products[0].system)
 
     payload = resp["payload"]
     payload = {
diff --git a/payments/factories.py b/payments/factories.py
index 8de51b87..be4cad6b 100644
--- a/payments/factories.py
+++ b/payments/factories.py
@@ -5,7 +5,7 @@
 from factory.django import DjangoModelFactory
 
 from payments import models
-from system_meta.factories import ProductFactory
+from system_meta.factories import IntegratedSystemFactory, ProductFactory
 from unified_ecommerce.factories import UserFactory
 
 FAKE = faker.Factory.create()
@@ -15,6 +15,7 @@ class BasketFactory(DjangoModelFactory):
     """Factory for Basket"""
 
     user = SubFactory(UserFactory)
+    integrated_system = SubFactory(IntegratedSystemFactory)
 
     class Meta:
         """Meta options for BasketFactory"""
diff --git a/payments/migrations/0004_remove_existing_baskets.py b/payments/migrations/0004_remove_existing_baskets.py
new file mode 100644
index 00000000..4e14f3e8
--- /dev/null
+++ b/payments/migrations/0004_remove_existing_baskets.py
@@ -0,0 +1,17 @@
+# Generated by Django 4.2.16 on 2024-10-16 18:16
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("payments", "0003_alter_order_state"),
+    ]
+
+    def _delete_existing_baskets(apps, scheme_editor):  # noqa: ARG002, N805
+        model = apps.get_model("payments", "basket")
+        model.objects.all().delete()
+
+    operations = [
+        migrations.RunPython(_delete_existing_baskets),
+    ]
diff --git a/payments/migrations/0005_basket_integrated_system_alter_basket_user.py b/payments/migrations/0005_basket_integrated_system_alter_basket_user.py
new file mode 100644
index 00000000..a7bb0241
--- /dev/null
+++ b/payments/migrations/0005_basket_integrated_system_alter_basket_user.py
@@ -0,0 +1,35 @@
+# Generated by Django 4.2.16 on 2024-10-16 18:16
+
+import django.db.models.deletion
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ("system_meta", "0005_integratedsystem_payment_process_redirect_url"),
+        ("payments", "0004_remove_existing_baskets"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="basket",
+            name="integrated_system",
+            field=models.ForeignKey(
+                on_delete=django.db.models.deletion.CASCADE,
+                related_name="basket",
+                to="system_meta.integratedsystem",
+            ),
+            preserve_default=False,
+        ),
+        migrations.AlterField(
+            model_name="basket",
+            name="user",
+            field=models.ForeignKey(
+                on_delete=django.db.models.deletion.CASCADE,
+                related_name="basket",
+                to=settings.AUTH_USER_MODEL,
+            ),
+        ),
+    ]
diff --git a/payments/models.py b/payments/models.py
index e9568627..834365e4 100644
--- a/payments/models.py
+++ b/payments/models.py
@@ -14,7 +14,7 @@
 from mitol.common.models import TimestampedModel
 from reversion.models import Version
 
-from system_meta.models import Product
+from system_meta.models import IntegratedSystem, Product
 from unified_ecommerce.constants import (
     POST_SALE_SOURCE_REDIRECT,
     TRANSACTION_TYPE_PAYMENT,
@@ -31,7 +31,10 @@
 class Basket(TimestampedModel):
     """Represents a User's basket."""
 
-    user = models.OneToOneField(User, on_delete=models.CASCADE, related_name="basket")
+    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name="basket")
+    integrated_system = models.ForeignKey(
+        IntegratedSystem, on_delete=models.CASCADE, related_name="basket"
+    )
 
     def compare_to_order(self, order):
         """
@@ -57,7 +60,7 @@ def get_products(self):
         return [item.product for item in self.basket_items.all()]
 
     @staticmethod
-    def establish_basket(request):
+    def establish_basket(request, integrated_system: IntegratedSystem):
         """
         Get or create the user's basket.
 
@@ -66,15 +69,22 @@ def establish_basket(request):
         system (IntegratedSystem): The system to associate with the basket.
         """
         user = request.user
-        (basket, is_new) = Basket.objects.filter(user=user).get_or_create(
-            defaults={"user": user}
-        )
+        (basket, is_new) = Basket.objects.filter(
+            user=user, integrated_system=integrated_system
+        ).get_or_create(defaults={"user": user, "integrated_system": integrated_system})
 
         if is_new:
             basket.save()
 
         return basket
 
+    constraints = [
+        models.UniqueConstraint(
+            fields=["user", "integrated_system"],
+            name="unique_user_integrated_system",
+        ),
+    ]
+
 
 class BasketItem(TimestampedModel):
     """Represents one or more products in a user's basket."""
diff --git a/payments/views/v0/__init__.py b/payments/views/v0/__init__.py
index 2a09c968..27fe1b43 100644
--- a/payments/views/v0/__init__.py
+++ b/payments/views/v0/__init__.py
@@ -106,7 +106,7 @@ def create_basket_from_product(request, system_slug: str, sku: str):
         Response: HTTP response
     """
     system = IntegratedSystem.objects.get(slug=system_slug)
-    basket = Basket.establish_basket(request)
+    basket = Basket.establish_basket(request, system)
     quantity = request.data.get("quantity", 1)
     checkout = request.data.get("checkout", False)
 
@@ -123,7 +123,7 @@ def create_basket_from_product(request, system_slug: str, sku: str):
     basket.refresh_from_db()
 
     if checkout:
-        return redirect("checkout_interstitial_page")
+        return redirect("checkout_interstitial_page", system_slug=system.slug)
 
     return Response(
         BasketWithProductSerializer(basket).data,
@@ -139,14 +139,18 @@ def create_basket_from_product(request, system_slug: str, sku: str):
 )
 @api_view(["DELETE"])
 @permission_classes([IsAuthenticated])
-def clear_basket(request):
+def clear_basket(request, system_slug: str):
     """
     Clear the basket for the current user.
 
+    Args:
+        system_slug (str): system slug
+
     Returns:
         Response: HTTP response
     """
-    basket = Basket.establish_basket(request)
+    system = IntegratedSystem.objects.get(slug=system_slug)
+    basket = Basket.establish_basket(request, system)
 
     basket.delete()
 
@@ -185,7 +189,8 @@ def start_checkout(self, request):
               ultimately POST to the actual payment processor.
         """
         try:
-            payload = api.generate_checkout_payload(request)
+            system = IntegratedSystem.objects.get(slug=self.kwargs["system_slug"])
+            payload = api.generate_checkout_payload(request, system)
         except ObjectDoesNotExist:
             return Response("No basket", status=status.HTTP_406_NOT_ACCEPTABLE)
 
diff --git a/payments/views/v0/urls.py b/payments/views/v0/urls.py
index 065c63bb..1755ee4f 100644
--- a/payments/views/v0/urls.py
+++ b/payments/views/v0/urls.py
@@ -19,7 +19,9 @@
 
 router.register(r"orders/history", OrderHistoryViewSet, basename="orderhistory_api")
 
-router.register(r"checkout", CheckoutApiViewSet, basename="checkout")
+router.register(
+    r"checkout/r'<str:system_slug>'", CheckoutApiViewSet, basename="checkout"
+)
 
 urlpatterns = [
     path(
@@ -28,7 +30,7 @@
         name="create_from_product",
     ),
     path(
-        "baskets/clear/",
+        "baskets/clear/<str:system_slug>/",
         clear_basket,
         name="clear_basket",
     ),