diff --git a/erpnext/controllers/accounts_controller.py b/erpnext/controllers/accounts_controller.py
index 346c4aa..c5390ff 100644
--- a/erpnext/controllers/accounts_controller.py
+++ b/erpnext/controllers/accounts_controller.py
@@ -44,7 +44,9 @@
 			self.set_total_in_words()
 
 		if self.doctype in ("Sales Invoice", "Purchase Invoice") and not self.is_return:
-			self.validate_payment_schedule()
+			if self.get("payment_schedule"):
+				self.set_due_date()
+				self.validate_payment_schedule()
 			self.validate_due_date()
 			self.validate_advance_entries()
 
@@ -626,6 +628,9 @@
 		else:
 			self.due_date = max([d.due_date for d in self.get("payment_schedule")])
 
+	def set_due_date(self):
+		self.due_date = max([d.due_date for d in self.get("payment_schedule")])
+
 	def validate_payment_schedule(self):
 		if self.due_date and getdate(self.due_date) < getdate(self.posting_date):
 			frappe.throw(_("Due Date cannot be before posting date"))
@@ -641,7 +646,6 @@
 			frappe.throw(_("Total Payment Amount in Payment Schdule must be equal to Grand Total"))
 
 
-
 @frappe.whitelist()
 def get_tax_rate(account_head):
 	return frappe.db.get_value("Account", account_head, ["tax_rate", "account_name"], as_dict=True)