diff --git a/InvenTree/InvenTree/models.py b/InvenTree/InvenTree/models.py
index 35ed5ccc0c..acfdad80fc 100644
--- a/InvenTree/InvenTree/models.py
+++ b/InvenTree/InvenTree/models.py
@@ -2,6 +2,7 @@ from __future__ import unicode_literals
 
 from django.db import models
 from django.contrib.contenttypes.models import ContentType
+from rest_framework.exceptions import ValidationError
 
 
 class Company(models.Model):
@@ -150,7 +151,7 @@ class InvenTreeTree(models.Model):
                 pass
             # Parent cannot be set to same ID (this would cause looping)
             elif val == self.id:
-                return
+                raise ValidationError("Category cannot set itself as parent")
             # Null parent is OK
             elif val is None:
                 pass
@@ -158,7 +159,7 @@ class InvenTreeTree(models.Model):
             else:
                 kids = self.getUniqueChildren()
                 if val in kids:
-                    return
+                    raise ValidationError("Category cannot set a child as parent")
 
         # Prohibit certain characters from tree node names
         elif attrname == 'name':
diff --git a/InvenTree/InvenTree/urls.py b/InvenTree/InvenTree/urls.py
index e50470dc1c..a81134e48f 100644
--- a/InvenTree/InvenTree/urls.py
+++ b/InvenTree/InvenTree/urls.py
@@ -8,6 +8,7 @@ from stock.urls import stock_urls, stock_loc_urls, stock_track_urls
 from project.urls import prj_urls, prj_part_urls, prj_cat_urls, prj_run_urls
 from supplier.urls import cust_urls, manu_urls, supplier_part_urls, price_break_urls, supplier_urls
 from track.urls import unique_urls, part_track_urls
+from users.urls import user_urls
 
 admin.site.site_header = "InvenTree Admin"
 
@@ -40,6 +41,9 @@ apipatterns = [
     url(r'^project-category/', include(prj_cat_urls)),
     url(r'^project-part/', include(prj_part_urls)),
     url(r'^project-run/', include(prj_run_urls)),
+
+    # User URLs
+    url(r'^user/', include(user_urls)),
 ]
 
 urlpatterns = [
diff --git a/InvenTree/stock/models.py b/InvenTree/stock/models.py
index 877661dd7f..c4be02eb63 100644
--- a/InvenTree/stock/models.py
+++ b/InvenTree/stock/models.py
@@ -2,6 +2,7 @@ from __future__ import unicode_literals
 from django.utils.translation import ugettext as _
 from django.db import models
 from django.core.validators import MinValueValidator
+from django.contrib.auth.models import User
 
 from supplier.models import SupplierPart
 from part.models import Part
@@ -29,6 +30,7 @@ class StockItem(models.Model):
 
     # last time the stock was checked / counted
     stocktake_date = models.DateField(blank=True, null=True)
+    stocktake_user = models.ForeignKey(User, on_delete=models.SET_NULL, blank=True, null=True)
 
     review_needed = models.BooleanField(default=False)
 
@@ -63,7 +65,7 @@ class StockItem(models.Model):
 
     infinite = models.BooleanField(default=False)
 
-    def stocktake(self, count):
+    def stocktake(self, count, user):
         """ Perform item stocktake.
         When the quantity of an item is counted,
         record the date of stocktake
@@ -76,27 +78,7 @@ class StockItem(models.Model):
 
         self.quantity = count
         self.stocktake_date = datetime.now().date()
-        self.save()
-
-    def take_stock(self, amount):
-        """ Take items from stock
-        This function can be called by initiating a ProjectRun,
-        or by manually taking the items from the stock location
-        """
-
-        if self.infinite:
-            return
-
-        amount = int(amount)
-        if amount < 0:
-            raise ValueError("Stock amount must be positive")
-
-        q = self.quantity - amount
-
-        if q < 0:
-            q = 0
-
-        self.quantity = q
+        self.stocktake_user = user
         self.save()
 
     def add_stock(self, amount):
@@ -119,6 +101,9 @@ class StockItem(models.Model):
         self.quantity = q
         self.save()
 
+    def take_stock(self, amount):
+        self.add_stock(-amount)
+
     def __str__(self):
         return "{n} x {part} @ {loc}".format(
             n=self.quantity,
diff --git a/InvenTree/stock/serializers.py b/InvenTree/stock/serializers.py
index e73be8531b..fc0c6979fe 100644
--- a/InvenTree/stock/serializers.py
+++ b/InvenTree/stock/serializers.py
@@ -18,6 +18,7 @@ class StockItemSerializer(serializers.HyperlinkedModelSerializer):
                   'notes',
                   'updated',
                   'stocktake_date',
+                  'stocktake_user',
                   'review_needed',
                   'expected_arrival')
 
diff --git a/InvenTree/stock/views.py b/InvenTree/stock/views.py
index 26d6aa1e74..4dab2f4546 100644
--- a/InvenTree/stock/views.py
+++ b/InvenTree/stock/views.py
@@ -62,7 +62,7 @@ class StockStocktakeEndpoint(generics.UpdateAPIView):
 
     def update(self, request, *args, **kwargs):
         object = self.get_object()
-        object.stocktake(request.data['quantity'])
+        object.stocktake(request.data['quantity'], request.user)
 
         serializer = self.get_serializer(object)
 
diff --git a/InvenTree/users/__init__.py b/InvenTree/users/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/InvenTree/users/admin.py b/InvenTree/users/admin.py
new file mode 100644
index 0000000000..b12fa73f94
--- /dev/null
+++ b/InvenTree/users/admin.py
@@ -0,0 +1,3 @@
+# -*- coding: utf-8 -*-
+# from __future__ import unicode_literals
+# from django.contrib import admin
diff --git a/InvenTree/users/apps.py b/InvenTree/users/apps.py
new file mode 100644
index 0000000000..251989770b
--- /dev/null
+++ b/InvenTree/users/apps.py
@@ -0,0 +1,8 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.apps import AppConfig
+
+
+class UsersConfig(AppConfig):
+    name = 'users'
diff --git a/InvenTree/users/models.py b/InvenTree/users/models.py
new file mode 100644
index 0000000000..40a96afc6f
--- /dev/null
+++ b/InvenTree/users/models.py
@@ -0,0 +1 @@
+# -*- coding: utf-8 -*-
diff --git a/InvenTree/users/serializers.py b/InvenTree/users/serializers.py
new file mode 100644
index 0000000000..01ce8f44b3
--- /dev/null
+++ b/InvenTree/users/serializers.py
@@ -0,0 +1,14 @@
+from rest_framework import serializers
+from django.contrib.auth.models import User
+
+
+class UserSerializer(serializers.HyperlinkedModelSerializer):
+    """ Serializer for a User
+    """
+
+    class Meta:
+        model = User
+        fields = ('username',
+                  'first_name',
+                  'last_name',
+                  'email',)
diff --git a/InvenTree/users/tests.py b/InvenTree/users/tests.py
new file mode 100644
index 0000000000..57c7c1fe6b
--- /dev/null
+++ b/InvenTree/users/tests.py
@@ -0,0 +1,4 @@
+# -*- coding: utf-8 -*-
+# from __future__ import unicode_literals
+
+# from django.test import TestCase
diff --git a/InvenTree/users/urls.py b/InvenTree/users/urls.py
new file mode 100644
index 0000000000..046cab9428
--- /dev/null
+++ b/InvenTree/users/urls.py
@@ -0,0 +1,9 @@
+from django.conf.urls import url
+
+from . import views
+
+user_urls = [
+    url(r'^(?P<pk>[0-9]+)/?$', views.UserDetail.as_view(), name='user-detail'),
+
+    url(r'^$', views.UserList.as_view()),
+]
diff --git a/InvenTree/users/views.py b/InvenTree/users/views.py
new file mode 100644
index 0000000000..20fee70caa
--- /dev/null
+++ b/InvenTree/users/views.py
@@ -0,0 +1,17 @@
+from rest_framework import generics, permissions
+from django.contrib.auth.models import User
+from .serializers import UserSerializer
+
+
+class UserDetail(generics.RetrieveAPIView):
+
+    queryset = User.objects.all()
+    serializer_class = UserSerializer
+    permission_classes = (permissions.IsAuthenticatedOrReadOnly,)
+
+
+class UserList(generics.ListAPIView):
+
+    queryset = User.objects.all()
+    serializer_class = UserSerializer
+    permission_classes = (permissions.IsAuthenticatedOrReadOnly,)