diff --git a/erpnext/controllers/taxes_and_totals.py b/erpnext/controllers/taxes_and_totals.py
index 54aee03e083..1fc8128d6ea 100644
--- a/erpnext/controllers/taxes_and_totals.py
+++ b/erpnext/controllers/taxes_and_totals.py
@@ -38,7 +38,9 @@ class calculate_taxes_and_totals:
 
 		self._items = self.filter_rows() if self.doc.doctype == "Quotation" else self.doc.get("items")
 
-		get_round_off_applicable_accounts(self.doc.company, frappe.flags.round_off_applicable_accounts)
+		get_round_off_applicable_accounts(
+			self.doc.company, frappe.flags.round_off_applicable_accounts, self.doc
+		)
 		self.calculate()
 
 	def filter_rows(self):
@@ -1128,14 +1130,14 @@ def get_itemised_tax_breakup_html(doc):
 
 
 @frappe.whitelist()
-def get_round_off_applicable_accounts(company, account_list):
+def get_round_off_applicable_accounts(company, account_list, doc=None):
 	# required to set correct region
 	with temporary_flag("company", company):
-		return get_regional_round_off_accounts(company, account_list)
+		return get_regional_round_off_accounts(company, account_list, doc)
 
 
 @erpnext.allow_regional
-def get_regional_round_off_accounts(company, account_list):
+def get_regional_round_off_accounts(company, account_list, doc=None):
 	pass
 
 
diff --git a/erpnext/controllers/tests/test_taxes_and_totals.py b/erpnext/controllers/tests/test_taxes_and_totals.py
index 504716f4684..715acf8782f 100644
--- a/erpnext/controllers/tests/test_taxes_and_totals.py
+++ b/erpnext/controllers/tests/test_taxes_and_totals.py
@@ -1,3 +1,5 @@
+from unittest.mock import patch
+
 import frappe
 from frappe.tests.utils import FrappeTestCase
 
@@ -6,6 +8,28 @@ from erpnext.selling.doctype.sales_order.test_sales_order import make_sales_orde
 
 
 class TestTaxesAndTotals(FrappeTestCase):
+	def test_regional_round_off_accounts(self):
+		"""
+		Regional overrides cannot extend the list in-place — the return
+		value must be assigned back to frappe.flags.round_off_applicable_accounts.
+		"""
+		test_account = "_Test Round Off Account"
+
+		def mock_regional(company, account_list: list, doc=None) -> list:
+			# Simulates a regional override
+			account_list.extend([test_account])
+			return account_list
+
+		so = make_sales_order(do_not_save=True)
+
+		with patch(
+			"erpnext.controllers.taxes_and_totals.get_regional_round_off_accounts",
+			mock_regional,
+		):
+			calculate_taxes_and_totals(so)
+
+		self.assertIn(test_account, frappe.flags.round_off_applicable_accounts)
+
 	def test_disabling_rounded_total_resets_base_fields(self):
 		"""Disabling rounded total should also clear base rounded values."""
 		so = make_sales_order(do_not_save=True)
diff --git a/erpnext/public/js/controllers/taxes_and_totals.js b/erpnext/public/js/controllers/taxes_and_totals.js
index 7b07c13bf11..0df4cabfb4f 100644
--- a/erpnext/public/js/controllers/taxes_and_totals.js
+++ b/erpnext/public/js/controllers/taxes_and_totals.js
@@ -207,7 +207,8 @@ erpnext.taxes_and_totals = class TaxesAndTotals extends erpnext.payments {
 				"method": "erpnext.controllers.taxes_and_totals.get_round_off_applicable_accounts",
 				"args": {
 					"company": me.frm.doc.company,
-					"account_list": frappe.flags.round_off_applicable_accounts
+					"account_list": frappe.flags.round_off_applicable_accounts,
+					"doc": me.frm.doc,
 				},
 				callback(r) {
 					if (r.message) {