[feature] Line discount (#12393)

* Add "discount" support to order line items

* Fix total_price annotation for ExtraLineItem

* Add regression tests

* Add frontend support

* Updated documentation

* Added docs

* Bump API version and CHANGELOG

* Remove 'total_price' annotation

- Can be achieved using in-memory python methods

* Apply fix for migration testing

* Revert "Apply fix for migration testing"

This reverts commit 8d9f2dce8c.

* Different approach

* Adjust playwright threshold

src/backend/InvenTree/InvenTree/api_version.py

@@ -1,11 +1,14 @@
 """InvenTree API version information."""
 
 # InvenTree API version
-INVENTREE_API_VERSION = 523
+INVENTREE_API_VERSION = 524
 """Increment this API version number whenever there is a significant change to the API that any clients need to know about."""
 
 INVENTREE_API_TEXT = """
 
+v524 -> 2026-07-20 : https://github.com/inventree/InvenTree/pull/12393
+    - Adds "discount" field to order line items (and extra line items)
+
 v523 -> 2026-07-14 : https://github.com/inventree/InvenTree/pull/12391
     - Adds "bulk delete" support for order line item API endpoints (PurchaseOrder / SalesOrder / ReturnOrder / TransferOrder)
     - Adds "bulk delete" support for order extra line item API endpoints

src/backend/InvenTree/generic/states/fields.py

@@ -3,6 +3,7 @@
 from collections.abc import Iterable
 from typing import Any, Optional
 
+from django.apps import apps as global_apps
 from django.core.exceptions import ObjectDoesNotExist
 from django.db import models
 from django.utils.encoding import force_str
@@ -117,11 +118,23 @@ class InvenTreeCustomStatusModelField(models.PositiveIntegerField):
         return name, path, args, kwargs
 
     def contribute_to_class(self, cls, name):
-        """Add the _custom_key field to the model."""
+        """Add the _custom_key field to the model.
+
+        Only auto-add the companion field for the 'live' app registry. Any other
+        registry (migration state, or the throwaway model registries that some
+        backends - e.g. SQLite's table-rebuild routine - construct internally)
+        either already has the field explicitly declared, or will get it via a
+        separate migration operation. Auto-adding it there too would create a
+        duplicate field on the model.
+        """
         cls._meta.supports_custom_status = True
 
-        if not hasattr(self, '_custom_key_field') and not hasattr(
-            cls, f'{name}_custom_key'
+        is_live_model = cls._meta.apps is global_apps
+
+        if (
+            is_live_model
+            and not hasattr(self, '_custom_key_field')
+            and not hasattr(cls, f'{name}_custom_key')
         ):
             self.add_field(cls, name)
 

src/backend/InvenTree/order/api.py

@@ -744,7 +744,6 @@ class PurchaseOrderLineItemList(
         'reference',
         'SKU',
         'IPN',
-        'total_price',
         'target_date',
         'order',
         'status',

src/backend/InvenTree/order/migrations/0121_add_line_item_discount.py

@@ -0,0 +1,119 @@
+# Generated by Django 5.2.15 on 2026-07-14 02:18
+
+import django.core.validators
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("order", "0120_purchaseorder_tags_returnorder_tags_salesorder_tags_and_more"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="purchaseorderextraline",
+            name="discount",
+            field=models.DecimalField(
+                decimal_places=2,
+                default=0,
+                help_text="Discount percentage applied to this line item (0-100)",
+                max_digits=5,
+                validators=[
+                    django.core.validators.MinValueValidator(0),
+                    django.core.validators.MaxValueValidator(100),
+                ],
+                verbose_name="Discount",
+            ),
+        ),
+        migrations.AddField(
+            model_name="purchaseorderlineitem",
+            name="discount",
+            field=models.DecimalField(
+                decimal_places=2,
+                default=0,
+                help_text="Discount percentage applied to this line item (0-100)",
+                max_digits=5,
+                validators=[
+                    django.core.validators.MinValueValidator(0),
+                    django.core.validators.MaxValueValidator(100),
+                ],
+                verbose_name="Discount",
+            ),
+        ),
+        migrations.AddField(
+            model_name="returnorderextraline",
+            name="discount",
+            field=models.DecimalField(
+                decimal_places=2,
+                default=0,
+                help_text="Discount percentage applied to this line item (0-100)",
+                max_digits=5,
+                validators=[
+                    django.core.validators.MinValueValidator(0),
+                    django.core.validators.MaxValueValidator(100),
+                ],
+                verbose_name="Discount",
+            ),
+        ),
+        migrations.AddField(
+            model_name="returnorderlineitem",
+            name="discount",
+            field=models.DecimalField(
+                decimal_places=2,
+                default=0,
+                help_text="Discount percentage applied to this line item (0-100)",
+                max_digits=5,
+                validators=[
+                    django.core.validators.MinValueValidator(0),
+                    django.core.validators.MaxValueValidator(100),
+                ],
+                verbose_name="Discount",
+            ),
+        ),
+        migrations.AddField(
+            model_name="salesorderextraline",
+            name="discount",
+            field=models.DecimalField(
+                decimal_places=2,
+                default=0,
+                help_text="Discount percentage applied to this line item (0-100)",
+                max_digits=5,
+                validators=[
+                    django.core.validators.MinValueValidator(0),
+                    django.core.validators.MaxValueValidator(100),
+                ],
+                verbose_name="Discount",
+            ),
+        ),
+        migrations.AddField(
+            model_name="salesorderlineitem",
+            name="discount",
+            field=models.DecimalField(
+                decimal_places=2,
+                default=0,
+                help_text="Discount percentage applied to this line item (0-100)",
+                max_digits=5,
+                validators=[
+                    django.core.validators.MinValueValidator(0),
+                    django.core.validators.MaxValueValidator(100),
+                ],
+                verbose_name="Discount",
+            ),
+        ),
+        migrations.AddField(
+            model_name="transferorderlineitem",
+            name="discount",
+            field=models.DecimalField(
+                decimal_places=2,
+                default=0,
+                help_text="Discount percentage applied to this line item (0-100)",
+                max_digits=5,
+                validators=[
+                    django.core.validators.MinValueValidator(0),
+                    django.core.validators.MaxValueValidator(100),
+                ],
+                verbose_name="Discount",
+            ),
+        ),
+    ]

src/backend/InvenTree/order/models.py

@@ -5,7 +5,7 @@ from typing import Any, Optional, TypedDict
 
 from django.contrib.auth.models import User
 from django.core.exceptions import ValidationError
-from django.core.validators import MinValueValidator
+from django.core.validators import MaxValueValidator, MinValueValidator
 from django.db import models, transaction
 from django.db.models import F, Q, QuerySet, Sum
 from django.db.models.functions import Coalesce
@@ -157,7 +157,11 @@ class TotalPriceMixin(models.Model):
                 continue
 
             try:
-                total += line.quantity * convert_money(line.price, target_currency)
+                total += (
+                    line.quantity
+                    * convert_money(line.price, target_currency)
+                    * (1 - line.discount / 100)
+                )
             except MissingRate:
                 log_error('order.calculate_total_price')
                 logger.exception("Missing exchange rate for '%s'", target_currency)
@@ -171,7 +175,11 @@ class TotalPriceMixin(models.Model):
                 continue
 
             try:
-                total += line.quantity * convert_money(line.price, target_currency)
+                total += (
+                    line.quantity
+                    * convert_money(line.price, target_currency)
+                    * (1 - line.discount / 100)
+                )
             except MissingRate:
                 # Record the error, try to press on
 
@@ -2109,11 +2117,20 @@ class OrderLineItem(InvenTree.models.InvenTreeMetadataModel):
         validators=[MinValueValidator(0)],
     )
 
+    discount = models.DecimalField(
+        verbose_name=_('Discount'),
+        help_text=_('Discount percentage applied to this line item (0-100)'),
+        default=0,
+        max_digits=5,
+        decimal_places=2,
+        validators=[MinValueValidator(0), MaxValueValidator(100)],
+    )
+
     @property
     def total_line_price(self):
-        """Return the total price for this line item."""
+        """Return the total price for this line item, after any discount is applied."""
         if self.price:
-            return self.quantity * self.price
+            return self.quantity * self.price * (1 - self.discount / 100)
 
     line = models.CharField(
         max_length=20,

src/backend/InvenTree/order/serializers.py

@@ -305,6 +305,8 @@ class AbstractLineItemSerializer(FilterableSerializerMixin, serializers.Serializ
         required=False, allow_null=True, label=_('Target Date')
     )
 
+    discount = InvenTreeDecimalField(required=False)
+
     project_code_label = common.filters.enable_project_label_filter()
 
     project_code_detail = common.filters.enable_project_code_filter()
@@ -322,6 +324,7 @@ class AbstractExtraLineSerializer(
             'pk',
             'line',
             'description',
+            'discount',
             'link',
             'notes',
             'order',
@@ -331,6 +334,7 @@ class AbstractExtraLineSerializer(
             'quantity',
             'reference',
             'target_date',
+            'total_price',
             # Filterable detail fields
             'order_detail',
             'project_code_label',
@@ -340,10 +344,16 @@ class AbstractExtraLineSerializer(
 
     quantity = serializers.FloatField()
 
+    discount = InvenTreeDecimalField(required=False)
+
     price = InvenTreeMoneySerializer(allow_null=True)
 
     price_currency = InvenTreeCurrencySerializer()
 
+    total_price = InvenTreeMoneySerializer(
+        source='total_line_price', allow_null=True, read_only=True
+    )
+
     project_code_label = common.filters.enable_project_label_filter()
 
     project_code_detail = common.filters.enable_project_code_filter()
@@ -355,6 +365,7 @@ class AbstractExtraLineMeta:
     fields = [
         'pk',
         'description',
+        'discount',
         'quantity',
         'reference',
         'notes',
@@ -363,6 +374,7 @@ class AbstractExtraLineMeta:
         'order_detail',
         'price',
         'price_currency',
+        'total_price',
         'link',
     ]
 
@@ -558,6 +570,7 @@ class PurchaseOrderLineItemSerializer(
         fields = AbstractLineItemSerializer.line_fields([
             'part',
             'build_order',
+            'discount',
             'overdue',
             'received',
             'purchase_price',
@@ -586,7 +599,6 @@ class PurchaseOrderLineItemSerializer(
     def annotate_queryset(queryset):
         """Add some extra annotations to this queryset.
 
-        - "total_price" = purchase_price * quantity
         - "overdue" status (boolean field)
         """
         queryset = queryset.prefetch_related(
@@ -602,12 +614,6 @@ class PurchaseOrderLineItemSerializer(
             'part__manufacturer_part__manufacturer',
         )
 
-        queryset = queryset.annotate(
-            total_price=ExpressionWrapper(
-                F('purchase_price') * F('quantity'), output_field=models.DecimalField()
-            )
-        )
-
         queryset = queryset.annotate(
             overdue=Case(
                 When(
@@ -648,7 +654,9 @@ class PurchaseOrderLineItemSerializer(
 
     overdue = serializers.BooleanField(read_only=True, allow_null=True)
 
-    total_price = serializers.FloatField(read_only=True)
+    total_price = InvenTreeMoneySerializer(
+        source='total_line_price', allow_null=True, read_only=True
+    )
 
     part_detail = OptionalField(
         serializer_class=PartBriefSerializer,
@@ -1234,6 +1242,7 @@ class SalesOrderLineItemSerializer(
         fields = AbstractLineItemSerializer.line_fields([
             'allocated',
             'customer_detail',
+            'discount',
             'overdue',
             'part',
             'part_detail',
@@ -2331,6 +2340,7 @@ class ReturnOrderLineItemSerializer(
             'item',
             'received_date',
             'outcome',
+            'discount',
             'price',
             'price_currency',
             # Filterable detail fields

src/backend/InvenTree/order/test_api.py

@@ -3579,6 +3579,79 @@ class ReturnOrderLineItemTests(InvenTreeAPITestCase):
         self.assertEqual(models.ReturnOrderExtraLine.objects.count(), n - 2)
 
 
+class ExtraLineTotalPriceTest(InvenTreeAPITestCase):
+    """Unit tests for the 'total_price' field on ExtraLine API endpoints.
+
+    Covers PurchaseOrderExtraLine, SalesOrderExtraLine and ReturnOrderExtraLine,
+    which all share the same 'total_price' field via AbstractExtraLineSerializer.
+    """
+
+    fixtures = [
+        'category',
+        'part',
+        'company',
+        'location',
+        'supplier_part',
+        'stock',
+        'order',
+        'sales_order',
+        'return_order',
+    ]
+
+    roles = ['purchase_order.change', 'sales_order.change', 'return_order.change']
+
+    def check_total_price(
+        self, order, extra_line_model, list_url_name, detail_url_name
+    ):
+        """Create an ExtraLine with a known price/quantity/discount, and check total_price."""
+        line = extra_line_model.objects.create(
+            order=order, quantity=5, price=Money(10, 'USD'), discount=20
+        )
+
+        # 5 * 10 = 50, less 20% discount = 40
+        expected = 40
+
+        # List endpoint
+        response = self.get(
+            reverse(list_url_name), {'order': order.pk}, expected_code=200
+        )
+        result = next(r for r in response.data if r['pk'] == line.pk)
+        self.assertEqual(float(result['total_price']), expected)
+
+        # Detail endpoint
+        response = self.get(
+            reverse(detail_url_name, kwargs={'pk': line.pk}), expected_code=200
+        )
+        self.assertEqual(float(response.data['total_price']), expected)
+
+    def test_po_extra_line_total_price(self):
+        """Check 'total_price' for a PurchaseOrderExtraLine."""
+        self.check_total_price(
+            models.PurchaseOrder.objects.get(pk=1),
+            models.PurchaseOrderExtraLine,
+            'api-po-extra-line-list',
+            'api-po-extra-line-detail',
+        )
+
+    def test_so_extra_line_total_price(self):
+        """Check 'total_price' for a SalesOrderExtraLine."""
+        self.check_total_price(
+            models.SalesOrder.objects.get(pk=1),
+            models.SalesOrderExtraLine,
+            'api-so-extra-line-list',
+            'api-so-extra-line-detail',
+        )
+
+    def test_return_order_extra_line_total_price(self):
+        """Check 'total_price' for a ReturnOrderExtraLine."""
+        self.check_total_price(
+            models.ReturnOrder.objects.get(pk=1),
+            models.ReturnOrderExtraLine,
+            'api-return-order-extra-line-list',
+            'api-return-order-extra-line-detail',
+        )
+
+
 class TransferOrderTest(OrderTest):
     """Tests for the TransferOrder API."""
 

src/frontend/src/components/tables/ColumnRenderers.tsx

@@ -473,6 +473,22 @@ export function DecimalColumn(props: TableColumn): TableColumn {
   };
 }
 
+export function PercentageColumn(props: TableColumn): TableColumn {
+  return {
+    sortable: true,
+    render: (record: any) => {
+      const value = resolveItem(record, props.accessor ?? '');
+
+      if (value == null || value === 0) {
+        return '-';
+      }
+
+      return `${formatDecimal(value)}%`;
+    },
+    ...props
+  };
+}
+
 export function DescriptionColumn(props: TableColumnProps): TableColumn {
   return {
     accessor: 'description',

src/frontend/src/forms/CommonForms.tsx

@@ -91,6 +91,7 @@ export function extraLineItemFields(): ApiFormFieldSet {
     quantity: {},
     price: {},
     price_currency: {},
+    discount: {},
     project_code: ProjectCodeField(),
     notes: {},
     link: {}

src/frontend/src/forms/PurchaseOrderForms.tsx

@@ -186,6 +186,7 @@ export function usePurchaseOrderLineItemFields({
         value: purchasePriceCurrency,
         onValueChange: setPurchasePriceCurrency
       },
+      discount: {},
       auto_pricing: {
         default: create !== false,
         value: autoPricing,

src/frontend/src/forms/ReturnOrderForms.tsx

@@ -133,6 +133,7 @@ export function useReturnOrderLineItemFields({
       },
       price: {},
       price_currency: {},
+      discount: {},
       project_code: ProjectCodeField(),
       target_date: {},
       notes: {},

src/frontend/src/forms/SalesOrderForms.tsx

@@ -197,6 +197,7 @@ export function useSalesOrderLineItemFields({
         value: partCurrency,
         onValueChange: setPartCurrency
       },
+      discount: {},
       project_code: ProjectCodeField(),
       target_date: {},
       notes: {},

src/frontend/src/tables/general/ExtraLineItemTable.tsx

@@ -19,6 +19,7 @@ import {
   LineItemColumn,
   LinkColumn,
   NoteColumn,
+  PercentageColumn,
   ProjectCodeColumn
 } from '../../components/tables/ColumnRenderers';
 import { InvenTreeTable } from '../../components/tables/InvenTreeTable';
@@ -69,13 +70,17 @@ export default function ExtraLineItemTable({
             currency: record.price_currency
           })
       },
+      PercentageColumn({
+        accessor: 'discount',
+        title: t`Discount`,
+        defaultVisible: false
+      }),
       {
         accessor: 'total_price',
         title: t`Total Price`,
         render: (record: any) =>
-          formatCurrency(record.price, {
-            currency: record.price_currency,
-            multiplier: record.quantity
+          formatCurrency(record.total_price, {
+            currency: record.price_currency
           })
       },
       ProjectCodeColumn({}),

src/frontend/src/tables/purchasing/PurchaseOrderLineItemTable.tsx

@@ -30,6 +30,7 @@ import {
   LocationColumn,
   NoteColumn,
   PartColumn,
+  PercentageColumn,
   ProjectCodeColumn,
   ReferenceColumn,
   TargetDateColumn
@@ -254,13 +255,17 @@ export function PurchaseOrderLineItemTable({
         accessor: 'purchase_price',
         title: t`Unit Price`
       }),
+      PercentageColumn({
+        accessor: 'discount',
+        title: t`Discount`,
+        defaultVisible: false
+      }),
       {
         accessor: 'total_price',
         title: t`Total Price`,
         render: (record: any) =>
-          formatCurrency(record.purchase_price, {
-            currency: record.purchase_price_currency,
-            multiplier: record.quantity
+          formatCurrency(record.total_price, {
+            currency: record.purchase_price_currency
           })
       },
       TargetDateColumn({}),

src/frontend/src/tables/sales/ReturnOrderLineItemTable.tsx

@@ -23,6 +23,7 @@ import {
   LinkColumn,
   NoteColumn,
   PartColumn,
+  PercentageColumn,
   ProjectCodeColumn,
   ReferenceColumn,
   StatusColumn,
@@ -148,6 +149,11 @@ export default function ReturnOrderLineItemTable({
         render: (record: any) =>
           formatCurrency(record.price, { currency: record.price_currency })
       },
+      PercentageColumn({
+        accessor: 'discount',
+        title: t`Discount`,
+        defaultVisible: false
+      }),
       DateColumn({
         accessor: 'target_date',
         title: t`Target Date`

src/frontend/src/tables/sales/SalesOrderLineItemTable.tsx

@@ -36,6 +36,7 @@ import {
   IPNColumn,
   LineItemColumn,
   LinkColumn,
+  PercentageColumn,
   ProjectCodeColumn,
   ReferenceColumn,
   RenderPartColumn,
@@ -121,13 +122,18 @@ export default function SalesOrderLineItemTable({
             currency: record.sale_price_currency
           })
       },
+      PercentageColumn({
+        accessor: 'discount',
+        title: t`Discount`,
+        defaultVisible: false
+      }),
       {
         accessor: 'total_price',
         title: t`Total Price`,
         render: (record: any) =>
           formatCurrency(record.sale_price, {
             currency: record.sale_price_currency,
-            multiplier: record.quantity
+            multiplier: record.quantity * (1 - (record.discount ?? 0) / 100)
           })
       },
       DateColumn({

src/frontend/tests/pui_login.spec.ts

@@ -157,7 +157,7 @@ test('Login - Cold vs Warm vs Hot Load', async ({ page }) => {
   // Note: Vite server in dev mode is significantly slower than production build
   const COLD_MS_THRESHOLD: number = 5000;
   const WARM_MS_THRESHOLD: number = 4000;
-  const HOT_MS_THRESHOLD: number = 3000;
+  const HOT_MS_THRESHOLD: number = 3500;
 
   const coldMs = await loginAndMeasure(page);