diff --git a/src/accounting/models.py b/src/accounting/models.py
index c5355f2..3d0fb2d 100644
--- a/src/accounting/models.py
+++ b/src/accounting/models.py
@@ -67,9 +67,8 @@ class Transaction(CreatedModifiedAbstract):
 class Order(CreatedModifiedAbstract):
     """An order.
 
-    Scoped out: Contents of invoices will have to be tracked either here or in
-    a separate Invoice model. This is undecided because we are not generating
-    invoices at the moment.
+    We assemble the order from a number of products. Once an order is paid, the contents should be
+    considered locked.
     """
 
     user = models.ForeignKey("auth.User", on_delete=models.PROTECT)
@@ -114,6 +113,32 @@ class Order(CreatedModifiedAbstract):
         return x.hexdigest()
 
 
+class Product(CreatedModifiedAbstract):
+    """A generic product, for instance a membership or a service fee."""
+
+    name = models.CharField(max_length=512)
+    price = MoneyField(max_digits=16, decimal_places=2)
+    vat = MoneyField(max_digits=16, decimal_places=2)
+
+    def __str__(self) -> str:
+        return self.name
+
+
+class OrderProduct(CreatedModifiedAbstract):
+    """When a product is ordered, we store the product on the order.
+
+    This includes pricing information.
+    """
+
+    order = models.ForeignKey(Order, on_delete=models.CASCADE, related_name="ordered_products")
+    product = models.ForeignKey(Product, related_name="ordered_products", on_delete=models.PROTECT)
+    price = MoneyField(max_digits=16, decimal_places=2)
+    vat = MoneyField(max_digits=16, decimal_places=2)
+
+    def __str__(self) -> str:
+        return f"{self.product.name}"
+
+
 class Payment(CreatedModifiedAbstract):
     """A payment is a transaction that is made to pay for an order."""
 
diff --git a/src/membership/models.py b/src/membership/models.py
index 502aa66..7e71393 100644
--- a/src/membership/models.py
+++ b/src/membership/models.py
@@ -133,9 +133,23 @@ class MembershipType(CreatedModifiedAbstract):
 
     name = models.CharField(verbose_name=_("name"), max_length=64)
 
+    product = models.ForeignKey("accounting.Product", on_delete=models.PROTECT)
+
+    current = models.BooleanField(default=False)
+
     class Meta:
         verbose_name = _("membership type")
         verbose_name_plural = _("membership types")
 
     def __str__(self) -> str:
         return self.name
+
+    def create_membership(self, user: User) -> Membership:
+        """Create a current membership for this type."""
+        from .selectors import get_current_subscription_period
+
+        return Membership.objects.create(
+            membership_type=self,
+            user=user,
+            period=get_current_subscription_period(),
+        )