diff --git a/uncloud_pay/models.py b/uncloud_pay/models.py
index ebc1c09..781cd95 100644
--- a/uncloud_pay/models.py
+++ b/uncloud_pay/models.py
@@ -254,8 +254,8 @@ class BillingAddress(models.Model):
 # VAT
 
 class VATRate(models.Model):
-    start_date = models.DateField(blank=True, null=True)
-    stop_date = models.DateField(blank=True, null=True)
+    starting_date = models.DateField(blank=True, null=True)
+    ending_date = models.DateField(blank=True, null=True)
     territory_codes = models.TextField(blank=True, default='')
     currency_code = models.CharField(max_length=10)
     rate = models.FloatField()
@@ -324,7 +324,6 @@ class Order(models.Model):
                                    null=True)
 
 
-
     @property
     def count_billed(self):
         """
@@ -345,6 +344,7 @@ class Order(models.Model):
     @property
     def is_recurring(self):
         return not self.recurring_period == RecurringPeriod.ONE_TIME
+
     @property
     def is_terminated(self):
         return self.ending_date != None and self.ending_date < timezone.now()
@@ -367,73 +367,24 @@ class Order(models.Model):
     def generate_initial_bill(self):
         return Bill.generate_for(self.starting_date.year, self.starting_date.month, self.owner)
 
-    # Used by uncloud_pay tests.
-    @property
-    def bills(self):
-        return Bill.objects.filter(order=self)
-
-    @staticmethod
-    def from_product(product, **kwargs):
-        # FIXME: this is only a workaround.
-        billing_address = BillingAddress.get_preferred_address_for(product.owner)
-        if billing_address == None:
-            raise Exception("Owner does not have a billing address!")
-
-        return Order(description=product.description,
-                one_time_price=product.one_time_price,
-                recurring_price=product.recurring_price,
-                billing_address=billing_address,
-                owner=product.owner,
-                **kwargs)
-
-
     @property
     def records(self):
         return OrderRecord.objects.filter(order=self)
 
-    # these are real fields!!!
-    # @property
-    # def one_time_price(self):
-    #     return reduce(lambda acc, record: acc + record.one_time_price, self.records, 0)
-
-    # @property
-    # def recurring_price(self):
-    #     return reduce(lambda acc, record: acc + record.recurring_price, self.records, 0)
-
-    # Used by uncloud_pay tests.
-    @property
-    def bills(self):
-        return Bill.objects.filter(order=self)
-
-    def add_record(self, one_time_price, recurring_price, description):
-      OrderRecord.objects.create(order=self,
-              one_time_price=one_time_price,
-              recurring_price=recurring_price,
-              description=description)
-
     def __str__(self):
         return f"Order {self.owner}-{self.id}"
 
-        # return "{} created at {}, {}->{}, recurring period {}. One time price {}, recurring price {}".format(
-        #     self.id, self.creation_date,
-        #     self.starting_date, self.ending_date,
-        #     self.recurring_period,
-        #     self.one_time_price,
-        #     self.recurring_price)
-
 
 class Bill(models.Model):
     owner = models.ForeignKey(get_user_model(),
             on_delete=models.CASCADE)
 
     creation_date = models.DateTimeField(auto_now_add=True)
-
-    # FIXME: this is a race condition, if ending_date is evaluated
-    # in the next month the bill spawns two months!
     starting_date = models.DateTimeField(default=start_of_this_month)
-    ending_date = models.DateTimeField(default=end_of_this_month)
+    ending_date = models.DateTimeField()
     due_date = models.DateField(default=default_payment_delay)
 
+    # what is valid for? should this be "final"?
     valid = models.BooleanField(default=True)
 
     # Mapping to BillRecords
@@ -448,15 +399,34 @@ class Bill(models.Model):
                                     name='one_bill_per_month_per_user')
         ]
 
-    # billing address and vat rate is the same for the whole bill
-    # @property
-    # def vat_rate(self):
-    #     return Decimal(VATRate.get_for_country(self.bill.billing_address.country))
-
-
     def __str__(self):
         return f"Bill {self.owner}-{self.id}"
 
+
+    @classmethod
+    def create_next_bill_for_user(cls, user):
+        last_bill = cls.objects.filter(owner=user).order_by('id').last()
+        all_orders = Order.objects.filter(owner=user).order_by('id')
+        first_order = all_orders.first()
+
+
+        # Calculate the start date
+        if last_bill:
+            starting_date = last_bill.end_date + datetime.timedelta(seconds=1)
+        else:
+            if first_order:
+                starting_date = first_order.starting_date
+            else:
+                starting_date = timezone.now()
+
+        ending_date = end_of_month(starting_date)
+
+        for order in all_orders:
+            # check if order needs to be billed
+            # check if order has previous billing record
+
+            pass
+
     @classmethod
     def create_all_bills(cls):
         for owner in get_user_model().objects.all():
@@ -539,10 +509,11 @@ class BillRecord(models.Model):
     order = models.ForeignKey(Order, on_delete=models.CASCADE)
 
     # How many times the order has been used in this record
-    quantity = models.IntegerField(default=1)
+    quantity = models.DecimalField(max_digits=19, decimal_places=10)
 
     # The timeframe the bill record is for can (and probably often will) differ
     # from the bill time
+
     creation_date = models.DateTimeField(auto_now_add=True)
     starting_date = models.DateTimeField()
     ending_date = models.DateTimeField()