fix: update item_tax_rate in backend

erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py

@@ -43,6 +43,7 @@
 from erpnext.stock.doctype.stock_reconciliation.test_stock_reconciliation import (
 	create_stock_reconciliation,
 )
+from erpnext.stock.get_item_details import get_item_tax_map
 from erpnext.stock.utils import get_incoming_rate, get_stock_balance
 
 
@@ -2879,6 +2880,49 @@ def test_item_tax_net_range(self):
 		sales_invoice.save()
 		self.assertEqual(sales_invoice.items[0].item_tax_template, "_Test Account Excise Duty @ 10 - _TC")
 
+	def test_item_tax_rate(self):
+		item = create_item("T Shirt")
+
+		item.set("taxes", [])
+		item.append(
+			"taxes",
+			{
+				"item_tax_template": "_Test Account Excise Duty @ 10 - _TC",
+				"minimum_net_rate": 0,
+				"maximum_net_rate": 500,
+			},
+		)
+
+		item.append(
+			"taxes",
+			{
+				"item_tax_template": "_Test Account Excise Duty @ 12 - _TC",
+				"minimum_net_rate": 501,
+				"maximum_net_rate": 1000,
+			},
+		)
+
+		item.save()
+
+		sales_invoice = create_sales_invoice(item="T Shirt", rate=700, do_not_submit=True)
+		item_tax_map = get_item_tax_map(
+			doc=sales_invoice,
+			tax_template=sales_invoice.items[0].item_tax_template,
+		)
+		self.assertEqual(sales_invoice.items[0].item_tax_template, "_Test Account Excise Duty @ 12 - _TC")
+		self.assertEqual(sales_invoice.items[0].item_tax_rate, item_tax_map)
+
+		# Apply discount
+		sales_invoice.apply_discount_on = "Net Total"
+		sales_invoice.discount_amount = 300
+		sales_invoice.save()
+		item_tax_map = get_item_tax_map(
+			doc=sales_invoice,
+			tax_template=sales_invoice.items[0].item_tax_template,
+		)
+		self.assertEqual(sales_invoice.items[0].item_tax_template, "_Test Account Excise Duty @ 10 - _TC")
+		self.assertEqual(sales_invoice.items[0].item_tax_rate, item_tax_map)
+
 	@IntegrationTestCase.change_settings("Selling Settings", {"enable_discount_accounting": 1})
 	def test_sales_invoice_with_discount_accounting_enabled(self):
 		discount_account = create_account(

erpnext/controllers/taxes_and_totals.py

@@ -18,7 +18,7 @@
 	validate_taxes_and_charges,
 )
 from erpnext.deprecation_dumpster import deprecated
-from erpnext.stock.get_item_details import ItemDetailsCtx, _get_item_tax_template
+from erpnext.stock.get_item_details import ItemDetailsCtx, _get_item_tax_template, get_item_tax_map
 from erpnext.utilities.regional import temporary_flag
 
 logger = frappe.logger(__name__)
@@ -74,6 +74,7 @@ def _calculate(self):
 		self.validate_conversion_rate()
 		self.calculate_item_values()
 		self.validate_item_tax_template()
+		self.update_item_tax_map()
 		self.initialize_taxes()
 		self.determine_exclusive_rate()
 		self.calculate_net_total()
@@ -140,6 +141,18 @@ def validate_item_tax_template(self):
 							)
 						)
 
+	def update_item_tax_map(self):
+		for item in self.doc.items:
+			if not item.get("item_tax_template"):
+				item.item_tax_rate = None
+				continue
+
+			item.item_tax_rate = get_item_tax_map(
+				doc=self.doc,
+				tax_template=item.item_tax_template,
+				as_json=True,
+			)
+
 	def validate_conversion_rate(self):
 		# validate conversion rate
 		company_currency = erpnext.get_company_currency(self.doc.company)