diff --git a/erpnext/controllers/selling_controller.py b/erpnext/controllers/selling_controller.py
index 7504746..515239a 100644
--- a/erpnext/controllers/selling_controller.py
+++ b/erpnext/controllers/selling_controller.py
@@ -416,26 +416,26 @@
 			return
 
 		for d in self.get('items'):
-			if self.doctype == "Sales Invoice":
-				e = [d.item_code, d.description, d.warehouse, d.sales_order or d.delivery_note, d.batch_no or '']
-				f = [d.item_code, d.description, d.sales_order or d.delivery_note]
+			if self.doctype in ["POS Invoice","Sales Invoice"]:
+				stock_items = [d.item_code, d.description, d.warehouse, d.sales_order or d.delivery_note, d.batch_no or '']
+				non_stock_items = [d.item_code, d.description, d.sales_order or d.delivery_note]
 			elif self.doctype == "Delivery Note":
-				e = [d.item_code, d.description, d.warehouse, d.against_sales_order or d.against_sales_invoice, d.batch_no or '']
-				f = [d.item_code, d.description, d.against_sales_order or d.against_sales_invoice]
+				stock_items = [d.item_code, d.description, d.warehouse, d.against_sales_order or d.against_sales_invoice, d.batch_no or '']
+				non_stock_items = [d.item_code, d.description, d.against_sales_order or d.against_sales_invoice]
 			elif self.doctype in ["Sales Order", "Quotation"]:
-				e = [d.item_code, d.description, d.warehouse, '']
-				f = [d.item_code, d.description]
+				stock_items = [d.item_code, d.description, d.warehouse, '']
+				non_stock_items = [d.item_code, d.description]
 
 			if frappe.db.get_value("Item", d.item_code, "is_stock_item") == 1:
-				if e in check_list:
+				if stock_items in check_list:
 					frappe.throw(_("Note: Item {0} entered multiple times").format(d.item_code))
 				else:
-					check_list.append(e)
+					check_list.append(stock_items)
 			else:
-				if f in chk_dupl_itm:
+				if non_stock_items in chk_dupl_itm:
 					frappe.throw(_("Note: Item {0} entered multiple times").format(d.item_code))
 				else:
-					chk_dupl_itm.append(f)
+					chk_dupl_itm.append(non_stock_items)
 
 	def validate_target_warehouse(self):
 		items = self.get("items") + (self.get("packed_items") or [])