diff --git a/erpnext/controllers/taxes_and_totals.py b/erpnext/controllers/taxes_and_totals.py
index 2d3b224b76f5..fc0ba56d1f4f 100644
--- a/erpnext/controllers/taxes_and_totals.py
+++ b/erpnext/controllers/taxes_and_totals.py
@@ -40,7 +40,7 @@ def filter_rows(self):
 		return items
 
 	def calculate(self):
-		if not len(self._items):
+		if not len(self.doc.items):
 			return
 
 		self.discount_amount_applied = False
@@ -95,7 +95,7 @@ def validate_item_tax_template(self):
 		if self.doc.get("is_return") and self.doc.get("return_against"):
 			return
 
-		for item in self._items:
+		for item in self.doc.items:
 			if item.item_code and item.get("item_tax_template"):
 				item_doc = frappe.get_cached_doc("Item", item.item_code)
 				args = {
@@ -154,7 +154,7 @@ def calculate_item_values(self):
 			return
 
 		if not self.discount_amount_applied:
-			for item in self._items:
+			for item in self.doc.items:
 				self.doc.round_floats_in(item)
 
 				if item.discount_percentage == 100:
@@ -258,7 +258,7 @@ def determine_exclusive_rate(self):
 		if not any(cint(tax.included_in_print_rate) for tax in self.doc.get("taxes")):
 			return
 
-		for item in self._items:
+		for item in self.doc.items:
 			item_tax_map = self._load_item_tax_rate(item.item_tax_rate)
 			cumulated_tax_fraction = 0
 			total_inclusive_tax_amount_per_qty = 0
diff --git a/erpnext/public/js/controllers/taxes_and_totals.js b/erpnext/public/js/controllers/taxes_and_totals.js
index adf05ffb154d..dc7a5a8eef1c 100644
--- a/erpnext/public/js/controllers/taxes_and_totals.js
+++ b/erpnext/public/js/controllers/taxes_and_totals.js
@@ -128,7 +128,7 @@ erpnext.taxes_and_totals = class TaxesAndTotals extends erpnext.payments {
 	calculate_item_values() {
 		var me = this;
 		if (!this.discount_amount_applied) {
-			for (const item of this.frm._items || []) {
+			for (const item of this.frm.doc.items || []) {
 				frappe.model.round_floats_in(item);
 				item.net_rate = item.rate;
 				item.qty = item.qty === undefined ? (me.frm.doc.is_return ? -1 : 1) : item.qty;
@@ -227,7 +227,7 @@ erpnext.taxes_and_totals = class TaxesAndTotals extends erpnext.payments {
 		});
 		if(has_inclusive_tax==false) return;
 
-		$.each(me.frm._items || [], function(n, item) {
+		$.each(this.frm.doc.items || [], function(n, item) {
 			var item_tax_map = me._load_item_tax_rate(item.item_tax_rate);
 			var cumulated_tax_fraction = 0.0;
 			var total_inclusive_tax_amount_per_qty = 0;
@@ -630,7 +630,7 @@ erpnext.taxes_and_totals = class TaxesAndTotals extends erpnext.payments {
 
 	_cleanup() {
 		this.frm.doc.base_in_words = this.frm.doc.in_words = "";
-		let items = this.frm._items;
+		let items = this.frm.doc.items;
 
 		if(items && items.length) {
 			if(!frappe.meta.get_docfield(items[0].doctype, "item_tax_amount", this.frm.doctype)) {
diff --git a/erpnext/selling/doctype/quotation/test_quotation.py b/erpnext/selling/doctype/quotation/test_quotation.py
index 7b66b7a251ad..9a31e335a05f 100644
--- a/erpnext/selling/doctype/quotation/test_quotation.py
+++ b/erpnext/selling/doctype/quotation/test_quotation.py
@@ -561,12 +561,50 @@ def test_alternative_items_with_service_items(self):
 				"description": "VAT",
 				"doctype": "Sales Taxes and Charges",
 				"rate": 10,
+				"included_in_print_rate": 1,
 			},
 		)
 		quotation.submit()
 
-		self.assertEqual(quotation.net_total, 290)
-		self.assertEqual(quotation.grand_total, 319)
+		self.assertEqual(round(quotation.items[1].net_rate, 2), 136.36)
+		self.assertEqual(round(quotation.items[1].amount, 2), 150)
+
+		self.assertEqual(round(quotation.items[2].net_rate, 2), 163.64)
+		self.assertEqual(round(quotation.items[2].amount, 2), 180)
+
+		self.assertEqual(round(quotation.net_total, 2), 263.64)
+		self.assertEqual(round(quotation.total_taxes_and_charges, 2), 26.36)
+		self.assertEqual(quotation.grand_total, 290)
+
+	def test_amount_calculation_for_alternative_items(self):
+		"""Make sure that the amount is calculated correctly for alternative items when the qty is changed."""
+		from erpnext.stock.doctype.item.test_item import make_item
+
+		item_list = []
+		stock_items = {
+			"_Test Simple Item 1": 100,
+			"_Test Alt 1": 120,
+		}
+
+		for item, rate in stock_items.items():
+			make_item(item, {"is_stock_item": 0})
+			item_list.append(
+				{
+					"item_code": item,
+					"qty": 1,
+					"rate": rate,
+					"is_alternative": "Alt" in item,
+				}
+			)
+
+		quotation = make_quotation(item_list=item_list, do_not_submit=1)
+
+		self.assertEqual(quotation.items[1].amount, 120)
+
+		quotation.items[1].qty = 2
+		quotation.save()
+
+		self.assertEqual(quotation.items[1].amount, 240)
 
 	def test_alternative_items_sales_order_mapping_with_stock_items(self):
 		from erpnext.selling.doctype.quotation.quotation import make_sales_order