diff --git a/erpnext/accounts/doctype/account/account.py b/erpnext/accounts/doctype/account/account.py
index 2f60dca..e067c70 100644
--- a/erpnext/accounts/doctype/account/account.py
+++ b/erpnext/accounts/doctype/account/account.py
@@ -165,7 +165,7 @@
 		# If outstanding greater than credit limit and not authorized person raise exception
 		if credit_limit > 0 and flt(total_outstanding) > credit_limit \
 				and not self.get_authorized_user():
-			throw(_("{0} Credit limit {0} crossed").format(_(credit_limit_from), credit_limit))
+			throw(_("{0} Credit limit {1} crossed").format(_(credit_limit_from), credit_limit))
 
 	def validate_due_date(self, posting_date, due_date):
 		credit_days = (self.credit_days or frappe.db.get_value("Company", self.company, "credit_days"))
diff --git a/erpnext/accounts/report/general_ledger/general_ledger.py b/erpnext/accounts/report/general_ledger/general_ledger.py
index dd80528..fcacf7c 100644
--- a/erpnext/accounts/report/general_ledger/general_ledger.py
+++ b/erpnext/accounts/report/general_ledger/general_ledger.py
@@ -20,6 +20,9 @@
 	return columns, res
 
 def validate_filters(filters, account_details):
+	if filters.get("account") and not account_details.get(filters.account):
+		frappe.throw(_("Account {0} does not exists").format(filters.account))
+
 	if filters.get("account") and filters.get("group_by_account") \
 			and account_details[filters.account].group_or_ledger == "Ledger":
 		frappe.throw(_("Can not filter based on Account, if grouped by Account"))
diff --git a/erpnext/buying/doctype/purchase_order/purchase_order.py b/erpnext/buying/doctype/purchase_order/purchase_order.py
index d9035f4..6c7c0c6 100644
--- a/erpnext/buying/doctype/purchase_order/purchase_order.py
+++ b/erpnext/buying/doctype/purchase_order/purchase_order.py
@@ -70,9 +70,14 @@
 	def validate_minimum_order_qty(self):
 		itemwise_min_order_qty = frappe._dict(frappe.db.sql("select name, min_order_qty from tabItem"))
 
+		itemwise_qty = frappe._dict()
 		for d in self.get("po_details"):
-			if flt(d.stock_qty) < flt(itemwise_min_order_qty.get(d.item_code)):
-				frappe.throw(_("Row #{0}: Ordered qty can not less than item's minimum order qty (defined in item master).").format(d.idx))
+			itemwise_qty.setdefault(d.item_code, 0)
+			itemwise_qty[d.item_code] += flt(d.stock_qty)
+
+		for item_code, qty in itemwise_qty.items():
+			if flt(qty) < flt(itemwise_min_order_qty.get(item_code)):
+				frappe.throw(_("Item #{0}: Ordered qty can not less than item's minimum order qty (defined in item master).").format(item_code))
 
 	def get_schedule_dates(self):
 		for d in self.get('po_details'):
diff --git a/erpnext/controllers/selling_controller.py b/erpnext/controllers/selling_controller.py
index dd58758..e758dd1 100644
--- a/erpnext/controllers/selling_controller.py
+++ b/erpnext/controllers/selling_controller.py
@@ -151,7 +151,7 @@
 
 				cumulated_tax_fraction += tax.tax_fraction_for_current_item
 
-			if cumulated_tax_fraction and not self.discount_amount_applied:
+			if cumulated_tax_fraction and not self.discount_amount_applied and item.qty:
 				item.base_amount = flt((item.amount * self.conversion_rate) /
 					(1 + cumulated_tax_fraction), self.precision("base_amount", item))
 
@@ -308,14 +308,23 @@
 		customer_account = frappe.db.get_value("Account", {"company": self.company,
 			"master_name": self.customer}, "name")
 		if customer_account:
-			total_outstanding = frappe.db.sql("""select
+			invoice_outstanding = frappe.db.sql("""select
 				sum(ifnull(debit, 0)) - sum(ifnull(credit, 0))
 				from `tabGL Entry` where account = %s""", customer_account)
-			total_outstanding = total_outstanding[0][0] if total_outstanding else 0
+			invoice_outstanding = flt(invoice_outstanding[0][0]) if invoice_outstanding else 0
 
-			outstanding_including_current = flt(total_outstanding) + flt(grand_total)
-			frappe.get_doc('Account', customer_account).run_method("check_credit_limit",
-				outstanding_including_current)
+			ordered_amount_to_be_billed = frappe.db.sql("""
+				select sum(grand_total*(100 - ifnull(per_billed, 0))/100)
+				from `tabSales Order`
+				where customer=%s and docstatus = 1
+				and ifnull(per_billed, 0) < 100 and status != 'Stopped'""", self.customer)
+
+			ordered_amount_to_be_billed = flt(ordered_amount_to_be_billed[0][0]) \
+				if ordered_amount_to_be_billed else 0.0
+
+			total_outstanding = invoice_outstanding + ordered_amount_to_be_billed
+
+			frappe.get_doc('Account', customer_account).check_credit_limit(total_outstanding)
 
 	def validate_max_discount(self):
 		for d in self.get(self.fname):
@@ -330,6 +339,9 @@
 			reserved_warehouse = ""
 			reserved_qty_for_main_item = 0
 
+			if not d.qty:
+				frappe.throw(_("Row {0}: Qty is mandatory").format(d.idx))
+
 			if self.doctype == "Sales Order":
 				if (frappe.db.get_value("Item", d.item_code, "is_stock_item") == 'Yes' or
 					self.has_sales_bom(d.item_code)) and not d.warehouse:
diff --git a/erpnext/manufacturing/doctype/production_order/production_order.py b/erpnext/manufacturing/doctype/production_order/production_order.py
index 1486d2a..99a248b 100644
--- a/erpnext/manufacturing/doctype/production_order/production_order.py
+++ b/erpnext/manufacturing/doctype/production_order/production_order.py
@@ -47,7 +47,7 @@
 
 				self.validate_production_order_against_so()
 			else:
-				frappe.throw(_("Sales Order {0} is not valid") % self.sales_order)
+				frappe.throw(_("Sales Order {0} is not valid").format(self.sales_order))
 
 	def validate_warehouse(self):
 		from erpnext.stock.utils import validate_warehouse_company
diff --git a/erpnext/stock/doctype/material_request/material_request.py b/erpnext/stock/doctype/material_request/material_request.py
index 89121e3..10b5114 100644
--- a/erpnext/stock/doctype/material_request/material_request.py
+++ b/erpnext/stock/doctype/material_request/material_request.py
@@ -287,15 +287,18 @@
 def get_material_requests_based_on_supplier(supplier):
 	supplier_items = [d[0] for d in frappe.db.get_values("Item",
 		{"default_supplier": supplier})]
-	material_requests = frappe.db.sql_list("""select distinct mr.name
-		from `tabMaterial Request` mr, `tabMaterial Request Item` mr_item
-		where mr.name = mr_item.parent
-		and mr_item.item_code in (%s)
-		and mr.material_request_type = 'Purchase'
-		and ifnull(mr.per_ordered, 0) < 99.99
-		and mr.docstatus = 1
-		and mr.status != 'Stopped'""" % ', '.join(['%s']*len(supplier_items)),
-		tuple(supplier_items))
+	if supplier_items:
+		material_requests = frappe.db.sql_list("""select distinct mr.name
+			from `tabMaterial Request` mr, `tabMaterial Request Item` mr_item
+			where mr.name = mr_item.parent
+			and mr_item.item_code in (%s)
+			and mr.material_request_type = 'Purchase'
+			and ifnull(mr.per_ordered, 0) < 99.99
+			and mr.docstatus = 1
+			and mr.status != 'Stopped'""" % ', '.join(['%s']*len(supplier_items)),
+			tuple(supplier_items))
+	else:
+		material_requests = []
 	return material_requests, supplier_items
 
 @frappe.whitelist()