diff --git a/erpnext/controllers/accounts_controller.py b/erpnext/controllers/accounts_controller.py
index 2deeebe70f7..e277602f0a3 100644
--- a/erpnext/controllers/accounts_controller.py
+++ b/erpnext/controllers/accounts_controller.py
@@ -708,22 +708,24 @@ class AccountsController(TransactionBase):
 	def group_similar_items(self):
 		group_item_qty = {}
 		group_item_amount = {}
+		# to update serial number in print
+		count = 0
 
 		for item in self.items:
 			group_item_qty[item.item_code] = group_item_qty.get(item.item_code, 0) + item.qty
 			group_item_amount[item.item_code] = group_item_amount.get(item.item_code, 0) + item.amount
 
 		duplicate_list = []
-
 		for item in self.items:
 			if item.item_code in group_item_qty:
+				count += 1
 				item.qty = group_item_qty[item.item_code]
 				item.amount = group_item_amount[item.item_code]
 				item.rate = flt(flt(item.amount) / flt(item.qty), item.precision("rate"))
+				item.idx = count
 				del group_item_qty[item.item_code]
 			else:
 				duplicate_list.append(item)
-
 		for item in duplicate_list:
 			self.remove(item)