diff --git a/InvenTree/InvenTree/views.py b/InvenTree/InvenTree/views.py
index 4fc4de20ae..16f77e5d9b 100644
--- a/InvenTree/InvenTree/views.py
+++ b/InvenTree/InvenTree/views.py
@@ -321,14 +321,14 @@ class AjaxCreateView(AjaxMixin, CreateView):
     - Handles form validation via AJAX POST requests
     """
 
-    def validate(self, cleaned_data, **kwargs):
+    def validate(self, request, form, cleaned_data, **kwargs):
         """
         Hook for performing any extra validation, over and above the regular form.is_valid
 
-        If any errors exist, raise a ValidationError
+        If any errors exist, add them to the form, using form.add_error
 
         """
-        return True
+        pass
 
     def pre_save(self, form, request, **kwargs):
         """
@@ -370,13 +370,10 @@ class AjaxCreateView(AjaxMixin, CreateView):
         valid = self.form.is_valid()
 
         # Perform any extra validation steps
-        if valid:
-            try:
-                valid = valid and self.validate(self.form.cleaned_data)
-            except ValidationError as e:
-                valid = False
-
-                self.form.add_error(None, e)
+        self.validate(request, self.form, self.form.cleaned_data)
+        
+        # Check if form is valid again (after performing any custom validation)
+        valid = self.form.is_valid()
 
         # Extra JSON data sent alongside form
         data = {
@@ -467,7 +464,7 @@ class AjaxDeleteView(AjaxMixin, UpdateView):
     """
 
     form_class = DeleteForm
-    ajax_form_title = "Delete Item"
+    ajax_form_title = _("Delete Item")
     ajax_template_name = "modal_delete_form.html"
     context_object_name = 'item'
 
@@ -516,7 +513,7 @@ class AjaxDeleteView(AjaxMixin, UpdateView):
         if confirmed:
             obj.delete()
         else:
-            form.errors['confirm_delete'] = ['Check box to confirm item deletion']
+            form.add_error('confirm_delete', _('Check box to confirm item deletion'))
             context[self.context_object_name] = self.get_object()
 
         data = {
@@ -531,7 +528,7 @@ class EditUserView(AjaxUpdateView):
     """ View for editing user information """
 
     ajax_template_name = "modal_form.html"
-    ajax_form_title = "Edit User Information"
+    ajax_form_title = _("Edit User Information")
     form_class = EditUserForm
 
     def get_object(self):
@@ -542,7 +539,7 @@ class SetPasswordView(AjaxUpdateView):
     """ View for setting user password """
 
     ajax_template_name = "InvenTree/password.html"
-    ajax_form_title = "Set Password"
+    ajax_form_title = _("Set Password")
     form_class = SetPasswordForm
 
     def get_object(self):
@@ -561,9 +558,9 @@ class SetPasswordView(AjaxUpdateView):
             # Passwords must match
 
             if not p1 == p2:
-                error = 'Password fields must match'
-                form.errors['enter_password'] = [error]
-                form.errors['confirm_password'] = [error]
+                error = _('Password fields must match')
+                form.add_error('enter_password', error)
+                form.add_error('confirm_password', error)
 
                 valid = False
 
diff --git a/InvenTree/build/views.py b/InvenTree/build/views.py
index 82620ed81f..6666089d11 100644
--- a/InvenTree/build/views.py
+++ b/InvenTree/build/views.py
@@ -74,7 +74,7 @@ class BuildCancel(AjaxUpdateView):
         if confirm:
             build.cancelBuild(request.user)
         else:
-            form.errors['confirm_cancel'] = [_('Confirm build cancellation')]
+            form.add_error('confirm_cancel', _('Confirm build cancellation'))
             valid = False
 
         data = {
@@ -152,8 +152,8 @@ class BuildAutoAllocate(AjaxUpdateView):
             build.auto_allocate(output)
             valid = True
         else:
-            form.errors['confirm'] = [_('Confirm stock allocation')]
-            form.non_field_errors = [_('Check the confirmation box at the bottom of the list')]
+            form.add_error('confirm', _('Confirm stock allocation'))
+            form.add_error(None, _('Check the confirmation box at the bottom of the list'))
 
         data = {
             'form_valid': valid,
@@ -205,10 +205,10 @@ class BuildOutputDelete(AjaxUpdateView):
                 build.deleteBuildOutput(output)
                 valid = True
             else:
-                form.non_field_errors = [_('Build or output not specified')]
+                form.add_error(None, _('Build or output not specified'))
         else:
-            form.errors['confirm'] = [_('Confirm unallocation of build stock')]
-            form.non_field_errors = [_('Check the confirmation box')]
+            form.add_error('confirm', _('Confirm unallocation of build stock'))
+            form.add_error(None, _('Check the confirmation box'))
 
         data = {
             'form_valid': valid,
@@ -271,8 +271,8 @@ class BuildUnallocate(AjaxUpdateView):
         valid = False
 
         if confirm is False:
-            form.errors['confirm'] = [_('Confirm unallocation of build stock')]
-            form.non_field_errors = [_('Check the confirmation box')]
+            form.add_error('confirm', _('Confirm unallocation of build stock'))
+            form.add_error(None, _('Check the confirmation box'))
         else:
             build.unallocateStock(output=output, part=part)
             valid = True
@@ -374,15 +374,13 @@ class BuildComplete(AjaxUpdateView):
         valid = False
 
         if confirm is False:
-            form.errors['confirm'] = [
-                _('Confirm completion of build'),
-            ]
+            form.add_error('confirm', _('Confirm completion of build'))
         else:
             try:
                 location = StockLocation.objects.get(id=loc_id)
                 valid = True
             except (ValueError, StockLocation.DoesNotExist):
-                form.errors['location'] = [_('Invalid location selected')]
+                form.add_error('location', _('Invalid location selected'))
 
             serials = []
 
@@ -399,24 +397,20 @@ class BuildComplete(AjaxUpdateView):
                         # Exctract a list of provided serial numbers
                         serials = ExtractSerialNumbers(sn, build.quantity)
 
-                        existing = []
-
-                        for serial in serials:
-                            if build.part.checkIfSerialNumberExists(serial):
-                                existing.append(serial)
+                        existing = build.part.find_conflicting_serial_numbers(serials)
 
                         if len(existing) > 0:
                             exists = ",".join([str(x) for x in existing])
-                            form.errors['serial_numbers'] = [_('The following serial numbers already exist: ({sn})'.format(sn=exists))]
+                            form.add_error('serial_numbers', _('The following serial numbers already exist: ({sn})'.format(sn=exists)))
                             valid = False
 
                     except ValidationError as e:
-                        form.errors['serial_numbers'] = e.messages
+                        form.add_error('serial_numbers', e.messages)
                         valid = False
 
             if valid:
                 if not build.completeBuild(location, serials, request.user):
-                    form.non_field_errors = [('Build could not be completed')]
+                    form.add_error(None, _('Build could not be completed'))
                     valid = False
 
         data = {
@@ -560,7 +554,7 @@ class BuildCreate(AjaxCreateView):
             'success': _('Created new build'),
         }
 
-    def validate(self, cleaned_data, **kwargs):
+    def validate(self, request, form, cleaned_data, **kwargs):
         """
         Perform extra form validation.
 
@@ -574,18 +568,29 @@ class BuildCreate(AjaxCreateView):
         if part.trackable:
             # For a trackable part, either batch or serial nubmber must be specified
             if not cleaned_data['serial_numbers']:
-                raise ValidationError({
-                    'serial_numbers': _('Trackable part must have serial numbers specified')
-                }) 
+                form.add_error('serial_numbers', _('Trackable part must have serial numbers specified'))
+            else:
+                # If serial numbers are set...
+                serials = cleaned_data['serial_numbers']
+                quantity = cleaned_data['quantity']
 
-            # If serial numbers are set...
-            serials = cleaned_data['serial_numbers']
-            quantity = cleaned_data['quantity']
+                # Check that the provided serial numbers are sensible
+                try:
+                    extracted = ExtractSerialNumbers(serials, quantity)                
+                except ValidationError as e:
+                    extracted = None
+                    form.add_error('serial_numbers', e.messages)
 
-            extracted = ExtractSerialNumbers(serials, quantity)
+                if extracted:
+                    # Check that the provided serial numbers are not duplicates
+                    conflicts = part.find_conflicting_serial_numbers(extracted)
 
-        # Ok, no errors...
-        return True
+                    if len(conflicts) > 0:
+                        msg = ",".join([str(c) for c in conflicts])
+                        form.add_error(
+                            'serial_numbers',
+                            _('Serial numbers already exist') + ': ' + msg
+                        )
         
     def post_save(self, **kwargs):
         """
diff --git a/InvenTree/order/views.py b/InvenTree/order/views.py
index e4645e0ae5..b4d1271752 100644
--- a/InvenTree/order/views.py
+++ b/InvenTree/order/views.py
@@ -415,7 +415,7 @@ class PurchaseOrderCancel(AjaxUpdateView):
         valid = False
 
         if not confirm:
-            form.errors['confirm'] = [_('Confirm order cancellation')]
+            form.add_error('confirm', _('Confirm order cancellation'))
         else:
             valid = True
 
@@ -448,13 +448,13 @@ class SalesOrderCancel(AjaxUpdateView):
         valid = False
 
         if not confirm:
-            form.errors['confirm'] = [_('Confirm order cancellation')]
+            form.add_error('confirm', _('Confirm order cancellation'))
         else:
             valid = True
 
         if valid:
             if not order.cancel_order():
-                form.non_field_errors = [_('Could not cancel order')]
+                form.add_error(None, _('Could not cancel order'))
                 valid = False
 
         data = {
@@ -484,7 +484,7 @@ class PurchaseOrderIssue(AjaxUpdateView):
         valid = False
 
         if not confirm:
-            form.errors['confirm'] = [_('Confirm order placement')]
+            form.add_error('confirm', _('Confirm order placement'))
         else:
             valid = True
 
@@ -558,13 +558,13 @@ class SalesOrderShip(AjaxUpdateView):
         valid = False
 
         if not confirm:
-            form.errors['confirm'] = [_('Confirm order shipment')]
+            form.add_error('confirm', _('Confirm order shipment'))
         else:
             valid = True
 
         if valid:
             if not order.ship_order(request.user):
-                form.non_field_errors = [_('Could not ship order')]
+                form.add_error(None, _('Could not ship order'))
                 valid = False
 
         data = {
@@ -1135,7 +1135,7 @@ class POLineItemCreate(AjaxCreateView):
             order = PurchaseOrder.objects.get(id=order_id)
         except (ValueError, PurchaseOrder.DoesNotExist):
             order = None
-            form.errors['order'] = [_('Invalid Purchase Order')]
+            form.add_error('order', _('Invalid Purchase Order'))
             valid = False
 
         try:
@@ -1143,12 +1143,12 @@ class POLineItemCreate(AjaxCreateView):
 
             if order is not None:
                 if not sp.supplier == order.supplier:
-                    form.errors['part'] = [_('Supplier must match for Part and Order')]
+                    form.add_error('part', _('Supplier must match for Part and Order'))
                     valid = False
 
         except (SupplierPart.DoesNotExist, ValueError):
             valid = False
-            form.errors['part'] = [_('Invalid SupplierPart selection')]
+            form.add_error('part', _('Invalid SupplierPart selection'))
 
         data = {
             'form_valid': valid,
diff --git a/InvenTree/part/models.py b/InvenTree/part/models.py
index 37b6d25cb8..b8bab70fb8 100644
--- a/InvenTree/part/models.py
+++ b/InvenTree/part/models.py
@@ -360,7 +360,7 @@ class Part(MPTTModel):
             # And recursively check too
             item.sub_part.checkAddToBOM(parent)
 
-    def checkIfSerialNumberExists(self, sn):
+    def checkIfSerialNumberExists(self, sn, exclude_self=False):
         """
         Check if a serial number exists for this Part.
 
@@ -369,10 +369,28 @@ class Part(MPTTModel):
         """
 
         parts = Part.objects.filter(tree_id=self.tree_id)
+
         stock = StockModels.StockItem.objects.filter(part__in=parts, serial=sn)
 
+        if exclude_self:
+            stock = stock.exclude(pk=self.pk)
+
         return stock.exists()
 
+    def find_conflicting_serial_numbers(self, serials):
+        """
+        For a provided list of serials, return a list of those which are conflicting.
+        """
+
+        conflicts = []
+
+        for serial in serials:
+            if self.checkIfSerialNumberExists(serial, exclude_self=True):
+                conflicts.append(serial)
+
+        return conflicts
+
+
     def getLatestSerialNumber(self):
         """
         Return the "latest" serial number for this Part.
diff --git a/InvenTree/part/views.py b/InvenTree/part/views.py
index ecb0932b0b..4194e01545 100644
--- a/InvenTree/part/views.py
+++ b/InvenTree/part/views.py
@@ -445,9 +445,9 @@ class PartDuplicate(AjaxCreateView):
                 confirmed = str2bool(request.POST.get('confirm_creation', False))
 
                 if not confirmed:
-                    form.errors['confirm_creation'] = ['Possible matches exist - confirm creation of new part']
-                    
-                    form.pre_form_warning = 'Possible matches exist - confirm creation of new part'
+                    msg = _('Possible matches exist - confirm creation of new part')
+                    form.add_error('confirm_creation', msg)                    
+                    form.pre_form_warning = msg
                     valid = False
 
         data = {
@@ -575,9 +575,10 @@ class PartCreate(AjaxCreateView):
                 confirmed = str2bool(request.POST.get('confirm_creation', False))
 
                 if not confirmed:
-                    form.errors['confirm_creation'] = ['Possible matches exist - confirm creation of new part']
+                    msg = _('Possible matches exist - confirm creation of new part')
+                    form.add_error('confirm_creation', msg)
                     
-                    form.pre_form_warning = 'Possible matches exist - confirm creation of new part'
+                    form.pre_form_warning = msg
                     valid = False
 
         data = {
@@ -862,7 +863,7 @@ class BomValidate(AjaxUpdateView):
         if confirmed:
             part.validate_bom(request.user)
         else:
-            form.errors['validate'] = ['Confirm that the BOM is valid']
+            form.add_error('validate', _('Confirm that the BOM is valid'))
 
         data = {
             'form_valid': confirmed
@@ -1001,7 +1002,7 @@ class BomUpload(InvenTreeRoleMixin, FormView):
         bom_file_valid = False
 
         if bom_file is None:
-            self.form.errors['bom_file'] = [_('No BOM file provided')]
+            self.form.add_error('bom_file', _('No BOM file provided'))
         else:
             # Create a BomUploadManager object - will perform initial data validation
             # (and raise a ValidationError if there is something wrong with the file)
@@ -1012,7 +1013,7 @@ class BomUpload(InvenTreeRoleMixin, FormView):
                 errors = e.error_dict
 
                 for k, v in errors.items():
-                    self.form.errors[k] = v
+                    self.form.add_error(k, v)
 
         if bom_file_valid:
             # BOM file is valid? Proceed to the next step!
diff --git a/InvenTree/stock/models.py b/InvenTree/stock/models.py
index 4b48e8138a..de87b1c5e7 100644
--- a/InvenTree/stock/models.py
+++ b/InvenTree/stock/models.py
@@ -822,14 +822,11 @@ class StockItem(MPTTModel):
             raise ValidationError({"quantity": _("Quantity does not match serial numbers")})
 
         # Test if each of the serial numbers are valid
-        existing = []
-
-        for serial in serials:
-            if self.part.checkIfSerialNumberExists(serial):
-                existing.append(serial)
+        existing = self.part.find_conflicting_serial_numbers(serials)
 
         if len(existing) > 0:
-            raise ValidationError({"serial_numbers": _("Serial numbers already exist: ") + str(existing)})
+            exists = ','.join([str(x) for x in existing])
+            raise ValidationError({"serial_numbers": _("Serial numbers already exist") + ': ' + exists})
 
         # Create a new stock item for each unique serial number
         for serial in serials:
diff --git a/InvenTree/stock/tests.py b/InvenTree/stock/tests.py
index 34fe8877f8..4632505831 100644
--- a/InvenTree/stock/tests.py
+++ b/InvenTree/stock/tests.py
@@ -407,6 +407,13 @@ class VariantTest(StockTest):
 
         self.assertEqual(chair.getLatestSerialNumber(), '22')
 
+        # Check for conflicting serial numbers
+        to_check = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+
+        conflicts = chair.find_conflicting_serial_numbers(to_check)
+
+        self.assertEqual(len(conflicts), 6)
+
         # Same operations on a sub-item
         variant = Part.objects.get(pk=10003)
         self.assertEqual(variant.getLatestSerialNumber(), '22')
diff --git a/InvenTree/stock/views.py b/InvenTree/stock/views.py
index a60ce6b55c..a0128b8318 100644
--- a/InvenTree/stock/views.py
+++ b/InvenTree/stock/views.py
@@ -417,8 +417,8 @@ class StockItemDeleteTestData(AjaxUpdateView):
         confirm = str2bool(request.POST.get('confirm', False))
 
         if confirm is not True:
-            form.errors['confirm'] = [_('Confirm test data deletion')]
-            form.non_field_errors = [_('Check the confirmation box')]
+            form.add_error('confirm', _('Confirm test data deletion'))
+            form.add_error(None, _('Check the confirmation box'))
         else:
             stock_item.test_results.all().delete()
             valid = True
@@ -918,7 +918,7 @@ class StockItemUninstall(AjaxView, FormMixin):
 
         if not confirmed:
             valid = False
-            form.errors['confirm'] = [_('Confirm stock adjustment')]
+            form.add_error('confirm', _('Confirm stock adjustment'))
 
         data = {
             'form_valid': valid,
@@ -1116,7 +1116,7 @@ class StockAdjust(AjaxView, FormMixin):
 
         if not confirmed:
             valid = False
-            form.errors['confirm'] = [_('Confirm stock adjustment')]
+            form.add_error('confirm', _('Confirm stock adjustment'))
 
         data = {
             'form_valid': valid,
@@ -1416,7 +1416,7 @@ class StockItemSerialize(AjaxUpdateView):
         try:
             numbers = ExtractSerialNumbers(serials, quantity)
         except ValidationError as e:
-            form.errors['serial_numbers'] = e.messages
+            form.add_error('serial_numbers', e.messages)
             valid = False
             numbers = []
         
@@ -1428,9 +1428,9 @@ class StockItemSerialize(AjaxUpdateView):
                 
                 for k in messages.keys():
                     if k in ['quantity', 'destination', 'serial_numbers']:
-                        form.errors[k] = messages[k]
+                        form.add_error(k, messages[k])
                     else:
-                        form.non_field_errors = [messages[k]]
+                        form.add_error(None, messages[k])
 
                 valid = False
 
@@ -1621,14 +1621,14 @@ class StockItemCreate(AjaxCreateView):
                 part = None
                 quantity = 1
                 valid = False
-                form.errors['quantity'] = [_('Invalid quantity')]
+                form.add_error('quantity', _('Invalid quantity'))
 
             if quantity < 0:
-                form.errors['quantity'] = [_('Quantity cannot be less than zero')]
+                form.add_error('quantity', _('Quantity cannot be less than zero'))
                 valid = False
 
             if part is None:
-                form.errors['part'] = [_('Invalid part selection')]
+                form.add_error('part', _('Invalid part selection'))
             else:
                 # A trackable part must provide serial numbesr
                 if part.trackable:
@@ -1641,15 +1641,14 @@ class StockItemCreate(AjaxCreateView):
                         try:
                             serials = ExtractSerialNumbers(sn, quantity)
 
-                            existing = []
-
-                            for serial in serials:
-                                if part.checkIfSerialNumberExists(serial):
-                                    existing.append(serial)
+                            existing = part.find_conflicting_serial_numbers(serial)
 
                             if len(existing) > 0:
                                 exists = ",".join([str(x) for x in existing])
-                                form.errors['serial_numbers'] = [_('The following serial numbers already exist: ({sn})'.format(sn=exists))]
+                                form.add_error(
+                                    'serial_numbers',
+                                    _('Serial numbers already exist') + ': ' + exists
+                                )
                                 valid = False
 
                             else:
@@ -1681,7 +1680,7 @@ class StockItemCreate(AjaxCreateView):
                                     valid = True
 
                         except ValidationError as e:
-                            form.errors['serial_numbers'] = e.messages
+                            form.add_error('serial_numbers', e.messages)
                             valid = False
 
                     else: