diff --git a/erpnext/controllers/accounts_controller.py b/erpnext/controllers/accounts_controller.py
index 86ceb2e..fe6b39d 100644
--- a/erpnext/controllers/accounts_controller.py
+++ b/erpnext/controllers/accounts_controller.py
@@ -1073,6 +1073,13 @@
 	data = json.loads(trans_items)
 	for d in data:
 		child_item = frappe.get_doc(parent_doctype + ' Item', d.get("docname"))
+
+		if parent_doctype == "Sales Order" and flt(d.get("qty")) < child_item.delivered_qty:
+			frappe.throw(_("Cannot set quantity less than delivered quantity"))
+
+		if parent_doctype == "Purchase Order" and flt(d.get("qty")) < child_item.received_qty:
+			frappe.throw(_("Cannot set quantity less than received quantity"))
+
 		child_item.qty = flt(d.get("qty"))
 
 		if child_item.billed_amt > (flt(d.get("rate")) * flt(d.get("qty"))):
diff --git a/erpnext/selling/doctype/sales_order/test_sales_order.py b/erpnext/selling/doctype/sales_order/test_sales_order.py
index 65e91bc..0eb19e3 100644
--- a/erpnext/selling/doctype/sales_order/test_sales_order.py
+++ b/erpnext/selling/doctype/sales_order/test_sales_order.py
@@ -286,6 +286,9 @@
 
 		self.assertEqual(get_reserved_qty(), existing_reserved_qty + 3)
 
+		trans_item = json.dumps([{'item_code' : '_Test Item', 'rate' : 200, 'qty' : 2, 'docname': so.items[0].name}])
+		self.assertRaises(frappe.ValidationError, update_child_qty_rate,'Sales Order', trans_item, so.name)
+
 	def test_warehouse_user(self):
 		frappe.permissions.add_user_permission("Warehouse", "_Test Warehouse 1 - _TC", "test@example.com")
 		frappe.permissions.add_user_permission("Warehouse", "_Test Warehouse 2 - _TC1", "test2@example.com")
@@ -760,7 +763,7 @@
 		})
 
 	so.delivery_date = add_days(so.transaction_date, 10)
- 
+
 	if not args.do_not_save:
 		so.insert()
 		if not args.do_not_submit: