Merge pull request #47985 from frappe/mergify/bp/version-15-hotfix/pr-47946

fix: patch and report for incorrect discount values (backport #47946)

erpnext/accounts/doctype/purchase_invoice/test_purchase_invoice.py

@@ -2806,6 +2806,17 @@ class TestPurchaseInvoice(FrappeTestCase, StockTestMixin):
 		# Test 4 - Since this PI is overbilled by 130% and only 120% is allowed, it will fail
 		self.assertRaises(frappe.ValidationError, pi.submit)
 
+	def test_discount_percentage_not_set_when_amount_is_manually_set(self):
+		pi = make_purchase_invoice(do_not_save=True)
+		discount_amount = 7
+		pi.discount_amount = discount_amount
+		pi.save()
+		self.assertEqual(pi.additional_discount_percentage, None)
+		pi.set_posting_time = 1
+		pi.posting_date = add_days(today(), -1)
+		pi.save()
+		self.assertEqual(pi.discount_amount, discount_amount)
+
 
 def set_advance_flag(company, flag, default_account):
 	frappe.db.set_value(

erpnext/accounts/report/calculated_discount_mismatch/calculated_discount_mismatch.js

@@ -0,0 +1,13 @@
+// Copyright (c) 2025, Frappe Technologies Pvt. Ltd. and contributors
+// For license information, please see license.txt
+
+// frappe.query_reports["Calculated Discount Mismatch"] = {
+// 	filters: [
+// 		{
+// 			"fieldname": "my_filter",
+// 			"label": __("My Filter"),
+// 			"fieldtype": "Data",
+// 			"reqd": 1,
+// 		},
+// 	],
+// };

erpnext/accounts/report/calculated_discount_mismatch/calculated_discount_mismatch.json

@@ -0,0 +1,38 @@
+{
+ "add_total_row": 0,
+ "add_translate_data": 0,
+ "columns": [],
+ "creation": "2025-06-06 17:09:50.681090",
+ "disabled": 0,
+ "docstatus": 0,
+ "doctype": "Report",
+ "filters": [],
+ "idx": 0,
+ "is_standard": "Yes",
+ "letter_head": "",
+ "letterhead": null,
+ "modified": "2025-06-06 18:09:18.221911",
+ "modified_by": "Administrator",
+ "module": "Accounts",
+ "name": "Calculated Discount Mismatch",
+ "owner": "Administrator",
+ "prepared_report": 0,
+ "ref_doctype": "Version",
+ "report_name": "Calculated Discount Mismatch",
+ "report_type": "Script Report",
+ "roles": [
+  {
+   "role": "System Manager"
+  },
+  {
+   "role": "Administrator"
+  },
+  {
+   "role": "Accounts Manager"
+  },
+  {
+   "role": "Accounts User"
+  }
+ ],
+ "timeout": 0
+}

erpnext/accounts/report/calculated_discount_mismatch/calculated_discount_mismatch.py

@@ -0,0 +1,174 @@
+# Copyright (c) 2025, Frappe Technologies Pvt. Ltd. and contributors
+# For license information, please see license.txt
+
+import json
+
+import frappe
+from frappe import _
+from frappe.query_builder import Order, Tuple
+from frappe.utils import flt
+from frappe.utils.formatters import format_value
+
+AFFECTED_DOCTYPES = frozenset(
+	(
+		"POS Invoice",
+		"Purchase Invoice",
+		"Sales Invoice",
+		"Purchase Order",
+		"Supplier Quotation",
+		"Quotation",
+		"Sales Order",
+		"Delivery Note",
+		"Purchase Receipt",
+	)
+)
+LAST_MODIFIED_DATE_THRESHOLD = "2025-05-30"
+
+
+def execute(filters=None):
+	columns = get_columns()
+	data = get_data()
+
+	return columns, data
+
+
+def get_columns():
+	return [
+		{
+			"fieldname": "doctype",
+			"label": _("Transaction Type"),
+			"fieldtype": "Link",
+			"options": "DocType",
+			"width": 120,
+		},
+		{
+			"fieldname": "docname",
+			"label": _("Transaction Name"),
+			"fieldtype": "Dynamic Link",
+			"options": "doctype",
+			"width": 150,
+		},
+		{
+			"fieldname": "actual_discount_percentage",
+			"label": _("Discount Percentage in Transaction"),
+			"fieldtype": "Percent",
+			"width": 180,
+		},
+		{
+			"fieldname": "actual_discount_amount",
+			"label": _("Discount Amount in Transaction"),
+			"fieldtype": "Currency",
+			"width": 180,
+		},
+		{
+			"fieldname": "suspected_discount_amount",
+			"label": _("Suspected Discount Amount"),
+			"fieldtype": "Currency",
+			"width": 180,
+		},
+	]
+
+
+def get_data():
+	transactions_with_discount_percentage = {}
+
+	for doctype in AFFECTED_DOCTYPES:
+		transactions = get_transactions_with_discount_percentage(doctype)
+
+		for transaction in transactions:
+			transactions_with_discount_percentage[(doctype, transaction.name)] = transaction
+
+	if not transactions_with_discount_percentage:
+		return []
+
+	VERSION = frappe.qb.DocType("Version")
+
+	versions = (
+		frappe.qb.from_(VERSION)
+		.select(VERSION.ref_doctype, VERSION.docname, VERSION.data)
+		.where(VERSION.creation > LAST_MODIFIED_DATE_THRESHOLD)
+		.where(Tuple(VERSION.ref_doctype, VERSION.docname).isin(list(transactions_with_discount_percentage)))
+		.where(
+			VERSION.data.like('%"discount\\_amount"%')
+			| VERSION.data.like('%"additional\\_discount\\_percentage"%')
+		)
+		.orderby(VERSION.creation, order=Order.desc)
+		.run(as_dict=True)
+	)
+
+	if not versions:
+		return []
+
+	version_map = {}
+	for version in versions:
+		key = (version.ref_doctype, version.docname)
+		if key not in version_map:
+			version_map[key] = []
+
+		version_map[key].append(version.data)
+
+	data = []
+	discount_amount_field_map = {
+		doctype: frappe.get_meta(doctype).get_field("discount_amount") for doctype in AFFECTED_DOCTYPES
+	}
+	for doc, versions in version_map.items():
+		for version_data in versions:
+			if '"additional_discount_percentage"' in version_data:
+				# don't consider doc if additional_discount_percentage is changed in newest version
+				break
+
+			version_data = json.loads(version_data)
+			changed_values = version_data.get("changed")
+			if not changed_values:
+				continue
+
+			discount_values = next((row for row in changed_values if row[0] == "discount_amount"), None)
+			if not discount_values:
+				continue
+
+			old = discount_values[1]
+			new = discount_values[2]
+			doctype = doc[0]
+			doc_values = transactions_with_discount_percentage.get(doc)
+			formatted_discount_amount = format_value(
+				doc_values.discount_amount,
+				df=discount_amount_field_map[doctype],
+				currency=doc_values.currency,
+			)
+
+			if new != formatted_discount_amount:
+				# if the discount amount in the version is not equal to the current value, skip
+				break
+
+			data.append(
+				{
+					"doctype": doctype,
+					"docname": doc_values.name,
+					"actual_discount_percentage": doc_values.additional_discount_percentage,
+					"actual_discount_amount": new,
+					"suspected_discount_amount": old,
+				}
+			)
+			break
+
+	return data
+
+
+def get_transactions_with_discount_percentage(doctype):
+	transactions = frappe.get_all(
+		doctype,
+		fields=[
+			"name",
+			"currency",
+			"additional_discount_percentage",
+			"discount_amount",
+		],
+		filters={
+			"docstatus": 1,
+			"additional_discount_percentage": [">", 0],
+			"discount_amount": ["!=", 0],
+			"modified": [">", LAST_MODIFIED_DATE_THRESHOLD],
+		},
+	)
+
+	return transactions

erpnext/change_log/v15/v15_64_0.md

@@ -0,0 +1,11 @@
+There was a bug in the **Additional Discount** functionality of ERPNext in **v15.64.0**. This has since been fixed.
+
+**If you've updated from a version older than v15.64.0, no action is needed on your side.**
+
+If you're updating from v15.64.0, the **Additional Discount Amount** in some transactions may differ from the value you entered. This only affects cases where **Additional Discount Amount** is manually entered. If it is computed from **Additional Discount Percentage** entered by you, there shouldn't be any issue.
+
+This report can help identify such transactions: [Calculated Discount Mismatch](/app/query-report/Calculated%20Discount%20Mismatch)
+
+Please review and amend these as necessary.
+
+We apologize for the inconvenience caused.

erpnext/patches.txt

@@ -262,6 +262,7 @@ erpnext.patches.v14_0.clear_reconciliation_values_from_singles
 execute:frappe.rename_doc("Report", "TDS Payable Monthly", "Tax Withholding Details", force=True)
 erpnext.patches.v14_0.update_proprietorship_to_individual
 erpnext.patches.v15_0.rename_subcontracting_fields
+erpnext.patches.v15_0.unset_incorrect_additional_discount_percentage
 
 [post_model_sync]
 erpnext.patches.v15_0.create_asset_depreciation_schedules_from_assets

erpnext/patches/v15_0/unset_incorrect_additional_discount_percentage.py

@@ -0,0 +1,87 @@
+import frappe
+from frappe import scrub
+from frappe.model.meta import get_field_precision
+from frappe.utils import flt
+from semantic_version import Version
+
+from erpnext.accounts.report.calculated_discount_mismatch.calculated_discount_mismatch import (
+	AFFECTED_DOCTYPES,
+	LAST_MODIFIED_DATE_THRESHOLD,
+)
+
+
+def execute():
+	# run this patch only if erpnext version before update is v15.64.0 or higher
+	version, git_branch = frappe.db.get_value(
+		"Installed Application",
+		{"app_name": "erpnext"},
+		["app_version", "git_branch"],
+	)
+
+	semantic_version = get_semantic_version(version)
+	if semantic_version and (
+		semantic_version.major < 15 or (git_branch == "version-15" and semantic_version.minor < 64)
+	):
+		return
+
+	for doctype in AFFECTED_DOCTYPES:
+		meta = frappe.get_meta(doctype)
+		filters = {
+			"modified": [">", LAST_MODIFIED_DATE_THRESHOLD],
+			"additional_discount_percentage": [">", 0],
+			"discount_amount": ["!=", 0],
+		}
+
+		# can't reverse calculate grand_total if shipping rule is set
+		if meta.has_field("shipping_rule"):
+			filters["shipping_rule"] = ["is", "not set"]
+
+		documents = frappe.get_all(
+			doctype,
+			fields=[
+				"name",
+				"additional_discount_percentage",
+				"discount_amount",
+				"apply_discount_on",
+				"grand_total",
+				"net_total",
+			],
+			filters=filters,
+		)
+
+		if not documents:
+			continue
+
+		precision = get_field_precision(frappe.get_meta(doctype).get_field("additional_discount_percentage"))
+		mismatched_documents = []
+
+		for doc in documents:
+			# we need grand_total before applying discount
+			doc.grand_total += doc.discount_amount
+			discount_applied_on = scrub(doc.apply_discount_on)
+			calculated_discount_amount = flt(
+				doc.additional_discount_percentage * doc.get(discount_applied_on) / 100,
+				precision,
+			)
+
+			# if difference is more than 0.02 (based on precision), unset the additional discount percentage
+			if abs(calculated_discount_amount - doc.discount_amount) > 2 / (10**precision):
+				mismatched_documents.append(doc.name)
+
+		if mismatched_documents:
+			# changing the discount percentage has no accounting effect
+			# so we can safely set it to 0 in the database
+			frappe.db.set_value(
+				doctype,
+				{"name": ["in", mismatched_documents]},
+				"additional_discount_percentage",
+				0,
+				update_modified=False,
+			)
+
+
+def get_semantic_version(version):
+	try:
+		return Version(version)
+	except Exception:
+		pass