Add "discount" support to order line items

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',
@@ -340,6 +343,8 @@ class AbstractExtraLineSerializer(
 
     quantity = serializers.FloatField()
 
+    discount = InvenTreeDecimalField(required=False)
+
     price = InvenTreeMoneySerializer(allow_null=True)
 
     price_currency = InvenTreeCurrencySerializer()
@@ -355,6 +360,7 @@ class AbstractExtraLineMeta:
     fields = [
         'pk',
         'description',
+        'discount',
         'quantity',
         'reference',
         'notes',
@@ -558,6 +564,7 @@ class PurchaseOrderLineItemSerializer(
         fields = AbstractLineItemSerializer.line_fields([
             'part',
             'build_order',
+            'discount',
             'overdue',
             'received',
             'purchase_price',
@@ -604,7 +611,10 @@ class PurchaseOrderLineItemSerializer(
 
         queryset = queryset.annotate(
             total_price=ExpressionWrapper(
-                F('purchase_price') * F('quantity'), output_field=models.DecimalField()
+                F('purchase_price')
+                * F('quantity')
+                * (1 - F('discount') / Decimal(100)),
+                output_field=models.DecimalField(),
             )
         )
 
@@ -1208,6 +1218,7 @@ class SalesOrderLineItemSerializer(
         fields = AbstractLineItemSerializer.line_fields([
             'allocated',
             'customer_detail',
+            'discount',
             'overdue',
             'part',
             'part_detail',
@@ -2305,6 +2316,7 @@ class ReturnOrderLineItemSerializer(
             'item',
             'received_date',
             'outcome',
+            'discount',
             'price',
             'price_currency',
             # Filterable detail fields