diff --git a/InvenTree/build/models.py b/InvenTree/build/models.py
index f5dd359a0b..aaeb33676d 100644
--- a/InvenTree/build/models.py
+++ b/InvenTree/build/models.py
@@ -25,8 +25,8 @@ from InvenTree.status_codes import BuildStatus, StockStatus
 from InvenTree.fields import InvenTreeURLField
 from InvenTree.helpers import decimal2string
 
-from stock.models import StockItem
-from part.models import Part, BomItem
+from stock import models as StockModels
+from part import models as PartModels
 
 
 class Build(MPTTModel):
@@ -465,7 +465,7 @@ class BuildItem(models.Model):
             if self.stock_item.serial and not self.quantity == 1:
                 errors['quantity'] = _('Quantity must be 1 for serialized stock')
 
-        except (StockItem.DoesNotExist, Part.DoesNotExist):
+        except (StockModels.StockItem.DoesNotExist, PartModels.Part.DoesNotExist):
             pass
 
         if len(errors) > 0:
diff --git a/InvenTree/part/models.py b/InvenTree/part/models.py
index a03f11cbfa..fb0ee6e1f7 100644
--- a/InvenTree/part/models.py
+++ b/InvenTree/part/models.py
@@ -13,6 +13,7 @@ from django.urls import reverse
 
 from django.db import models, transaction
 from django.db.models import Sum
+from django.db.models.functions import Coalesce
 from django.db.models import prefetch_related_objects
 from django.core.validators import MinValueValidator
 
@@ -41,6 +42,8 @@ from InvenTree.helpers import decimal2string, normalize
 
 from InvenTree.status_codes import BuildStatus, StockStatus, PurchaseOrderStatus
 
+from build import models as BuildModels
+from order import models as OrderModels
 from company.models import SupplierPart
 from stock import models as StockModels
 
@@ -502,8 +505,7 @@ class Part(models.Model):
         """
 
         total = self.total_stock
-
-        total -= self.allocation_count
+        total -= self.allocation_count()
 
         return max(total, 0)
 
@@ -594,46 +596,48 @@ class Part(models.Model):
 
         return quantity
 
-    @property
-    def build_allocation(self):
-        """ Return list of builds to which this part is allocated
+    def build_order_allocations(self):
+        """
+        Return all 'BuildItem' objects which allocate this part to Build objects
         """
 
-        builds = []
+        return BuildModels.BuildItem.objects.filter(stock_item__part__id=self.id)
 
-        for item in self.used_in.all().prefetch_related('part__builds'):
-
-            active = item.part.active_builds
-            
-            for build in active:
-                b = {}
-
-                b['build'] = build
-                b['quantity'] = item.quantity * build.quantity
-
-                builds.append(b)
-
-        prefetch_related_objects(builds, 'build_items')
-
-        return builds
-
-    @property
-    def allocated_build_count(self):
-        """ Return the total number of this part that are allocated for builds
+    def build_order_allocation_count(self):
+        """
+        Return the total amount of this part allocated to build orders
         """
 
-        return sum([a['quantity'] for a in self.build_allocation])
+        query = self.build_order_allocations().aggregate(total=Coalesce(Sum('quantity'), 0))
+
+        return query['total']
+
+    def sales_order_allocations(self):
+        """
+        Return all sales-order-allocation objects which allocate this part to a SalesOrder
+        """
+
+        return OrderModels.SalesOrderAllocation.objects.filter(item__part__id=self.id)
+
+    def sales_order_allocation_count(self):
+        """
+        Return the tutal quantity of this part allocated to sales orders
+        """
+
+        query = self.sales_order_allocations().aggregate(total=Coalesce(Sum('quantity'), 0))
+
+        return query['total']
+
 
-    @property
     def allocation_count(self):
-        """ Return true if any of this part is allocated:
-
-        - To another build
-        - To a customer order
+        """
+        Return the total quantity of stock allocated for this part,
+        against both build orders and sales orders.
         """
 
         return sum([
-            self.allocated_build_count,
+            self.build_order_allocation_count(),
+            self.sales_order_allocation_count(),
         ])
 
     @property
@@ -645,7 +649,7 @@ class Part(models.Model):
         - belongs_to is None
         """
 
-        return self.stock_items.filter(StockModels.StockItem.IN_STOCK_FILTER).exclude(status__in=StockStatus.UNAVAILABLE_CODES)
+        return self.stock_items.filter(StockModels.StockItem.IN_STOCK_FILTER)
 
     @property
     def total_stock(self):
diff --git a/InvenTree/stock/models.py b/InvenTree/stock/models.py
index 2261d8ad23..c9e4c75336 100644
--- a/InvenTree/stock/models.py
+++ b/InvenTree/stock/models.py
@@ -31,7 +31,7 @@ from InvenTree.models import InvenTreeTree
 from InvenTree.fields import InvenTreeURLField
 
 from part import models as PartModels
-from order.models import PurchaseOrder, SalesOrder
+from order import models as OrderModels
 
 
 class StockLocation(InvenTreeTree):
@@ -134,7 +134,12 @@ class StockItem(MPTTModel):
     """
 
     # A Query filter which will be re-used in multiple places to determine if a StockItem is actually "in stock"
-    IN_STOCK_FILTER = Q(sales_order=None, build_order=None, belongs_to=None)
+    IN_STOCK_FILTER = Q(
+        sales_order=None,
+        build_order=None,
+        belongs_to=None,
+        status__in=StockStatus.AVAILABLE_CODES
+    )
 
     def save(self, *args, **kwargs):
         if not self.pk:
@@ -393,7 +398,7 @@ class StockItem(MPTTModel):
     )
 
     purchase_order = models.ForeignKey(
-        PurchaseOrder,
+        'order.PurchaseOrder',
         on_delete=models.SET_NULL,
         verbose_name=_('Source Purchase Order'),
         related_name='stock_items',
@@ -402,7 +407,7 @@ class StockItem(MPTTModel):
     )
 
     sales_order = models.ForeignKey(
-        SalesOrder,
+        'order.SalesOrder',
         on_delete=models.SET_NULL,
         verbose_name=_("Destination Sales Order"),
         related_name='stock_items',