diff --git a/erpnext/accounts/doctype/payment_entry/payment_entry.py b/erpnext/accounts/doctype/payment_entry/payment_entry.py
index 72ebce2..ca247ef 100644
--- a/erpnext/accounts/doctype/payment_entry/payment_entry.py
+++ b/erpnext/accounts/doctype/payment_entry/payment_entry.py
@@ -541,11 +541,14 @@
 
 	return negative_outstanding_invoices + outstanding_invoices + orders_to_be_billed
 
+
 def get_orders_to_be_billed(posting_date, party_type, party, party_account_currency, company_currency):
 	if party_type == "Customer":
 		voucher_type = 'Sales Order'
+		payment_dr_or_cr = "credit_in_account_currency - debit_in_account_currency"
 	elif party_type == "Supplier":
 		voucher_type = 'Purchase Order'
+		payment_dr_or_cr = "debit_in_account_currency - credit_in_account_currency"
 	elif party_type == "Employee":
 		voucher_type = None
 
@@ -554,26 +557,93 @@
 		ref_field = "base_grand_total" if party_account_currency == company_currency else "grand_total"
 
 		orders = frappe.db.sql("""
+					select
+						name as voucher_no,
+						{ref_field} as invoice_amount,
+						({ref_field} - advance_paid) as outstanding_amount,
+						transaction_date as posting_date
+					from
+						`tab{voucher_type}`
+					where
+						{party_type} = %s
+						and docstatus = 1
+						and ifnull(status, "") != "Closed"
+						and {ref_field} > advance_paid
+						and abs(100 - per_billed) > 0.01
+					order by
+						transaction_date, name
+					""".format(**{
+			"ref_field": ref_field,
+			"voucher_type": voucher_type,
+			"party_type": scrub(party_type)
+		}), party, as_dict=True)
+
+	if voucher_type and party_type is not "Employee":
+		ref_field = "base_grand_total" if party_account_currency == company_currency else "grand_total"
+
+		# find orders without considering if they have Payment Schedule
+		orders_without_schedule = frappe.db.sql("""
+					select
+						name as voucher_no,
+						{ref_field} as invoice_amount,
+						({ref_field} - advance_paid) as outstanding_amount,
+						transaction_date as posting_date
+					from
+						`tab{voucher_type}`
+					where
+						{party_type} = %s
+						and docstatus = 1
+						and ifnull(status, "") != "Closed"
+						and {ref_field} > advance_paid
+						and abs(100 - per_billed) > 0.01
+					order by
+						transaction_date, name
+					""".format(**{
+			"ref_field": ref_field,
+			"voucher_type": voucher_type,
+			"party_type": scrub(party_type)
+		}), party, as_dict=True)
+
+	# find orders considering if they have Payment Schedule
+	if voucher_type and party_type is not "Employee":
+		ref_field = "base_grand_total" if party_account_currency == company_currency else "grand_total"
+
+		orders_with_schedule = frappe.db.sql("""
 			select
-				name as voucher_no,
-				{ref_field} as invoice_amount,
-				({ref_field} - advance_paid) as outstanding_amount,
-				transaction_date as posting_date
+				VT.name as voucher_no,
+				PS.payment_amount as invoice_amount,
+				PS.payment_amount - (select
+										ifnull(sum({payment_dr_or_cr}), 0)
+										from `tabGL Entry`
+										where 
+											against_voucher = VT.name
+											and due_date = PS.due_date
+									) as outstanding_amount,
+				VT.transaction_date as posting_date,
+				PS.due_date
 			from
-				`tab{voucher_type}`
+				`tab{voucher_type}` VT
+			join 
+				`tabPayment Schedule` PS on VT.name = PS.parent
 			where
 				{party_type} = %s
-				and docstatus = 1
+				and VT.docstatus = 1
 				and ifnull(status, "") != "Closed"
 				and {ref_field} > advance_paid
 				and abs(100 - per_billed) > 0.01
 			order by
-				transaction_date, name
+				VT.transaction_date, VT.name
 			""".format(**{
 				"ref_field": ref_field,
 				"voucher_type": voucher_type,
-				"party_type": scrub(party_type)
-			}), party, as_dict = True)
+				"party_type": scrub(party_type),
+				"payment_dr_or_cr": payment_dr_or_cr
+			}), party, as_dict=True)
+
+	# reconcile both results such that we have a list that contains unique entries.
+	# Where both lists contain a record that is common, we select the one with
+	# linked Payment Schedule
+	orders = _merge_query_results(orders_without_schedule, orders_with_schedule, 'voucher_no')
 
 	order_list = []
 	for d in orders:
@@ -585,6 +655,33 @@
 
 	return order_list
 
+
+def _merge_query_results(result1, result2, dict_key):
+	"""
+	Merges two list of query results that are dictionaries.
+	For every item in result1 that is found in result2, the item is removed from
+	result1. At the end of processing result1, result1 and result2 are concatenated
+	and returned.
+
+	:param result1: List of dict
+	:param result2: List of dict
+	:return: List of dict
+	"""
+	for item in result1[:]:
+		found = False
+		for item2 in result2:
+			if item[dict_key] == item2[dict_key]:
+				found = True
+				break
+
+		if found:
+			result1.remove(item)
+
+	final_result = result1 + result2
+
+	return final_result
+
+
 def get_negative_outstanding_invoices(party_type, party, party_account, party_account_currency, company_currency):
 	voucher_type = "Sales Invoice" if party_type == "Customer" else "Purchase Invoice"
 	if party_account_currency == company_currency:
@@ -614,6 +711,7 @@
 			"party_account": "debit_to" if party_type == "Customer" else "credit_to"
 		}), (party, party_account), as_dict=True)
 
+
 @frappe.whitelist()
 def get_party_details(company, party_type, party, date):
 	if not frappe.db.exists(party_type, party):
@@ -635,6 +733,7 @@
 		"account_balance": account_balance
 	}
 
+
 @frappe.whitelist()
 def get_account_details(account, date):
 	frappe.has_permission('Payment Entry', throw=True)
@@ -644,6 +743,7 @@
 		"account_type": frappe.db.get_value("Account", account, "account_type")
 	})
 
+
 @frappe.whitelist()
 def get_company_defaults(company):
 	fields = ["write_off_account", "exchange_gain_loss_account", "cost_center"]
@@ -656,6 +756,7 @@
 
 	return ret
 
+
 @frappe.whitelist()
 def get_reference_details(reference_doctype, reference_name, party_account_currency):
 	total_amount = outstanding_amount = exchange_rate = None
@@ -701,6 +802,7 @@
 		"exchange_rate": exchange_rate
 	})
 
+
 @frappe.whitelist()
 def get_payment_entry(dt, dn, party_amount=None, bank_account=None, bank_amount=None):
 	doc = frappe.get_doc(dt, dn)
diff --git a/erpnext/controllers/accounts_controller.py b/erpnext/controllers/accounts_controller.py
index 10e1d92..0c36c6a 100644
--- a/erpnext/controllers/accounts_controller.py
+++ b/erpnext/controllers/accounts_controller.py
@@ -71,6 +71,7 @@
 		self.validate_advance_entries()
 
 	def validate_non_invoice_documents_schedule(self):
+		self.validate_payment_schedule_dates()
 		self.validate_invoice_portion()
 		self.set_payment_schedule()
 		self.validate_payment_schedule_amount()
@@ -672,15 +673,15 @@
 	def validate_payment_schedule_dates(self):
 		dates = []
 		li = []
-		if self.due_date and getdate(self.due_date) < getdate(self.posting_date):
-			frappe.throw(_("Due Date cannot be before posting date"))
+		if self.get('posting_date'):
+			if self.due_date and getdate(self.due_date) < getdate(self.posting_date):
+				frappe.throw(_("Due Date cannot be before posting date"))
 
 		for d in self.get("payment_schedule"):
-			if getdate(d.due_date) < getdate(self.posting_date):
+			if self.get('posting_date') and getdate(d.due_date) < getdate(self.posting_date):
 				frappe.throw(_("Row {0}: Due Date cannot be before posting date").format(d.idx))
 			elif d.due_date in dates:
 				li.append('{0} in row {1}'.format(d.due_date, d.idx))
-				# frappe.throw(_("Row {0}: Duplicate due date found").format(d.idx))
 			dates.append(d.due_date)
 
 		if li: