added debit and credit note status
diff --git a/erpnext/controllers/status_updater.py b/erpnext/controllers/status_updater.py
index cb783b4..fcddc8f 100644
--- a/erpnext/controllers/status_updater.py
+++ b/erpnext/controllers/status_updater.py
@@ -44,7 +44,9 @@
 	"Sales Invoice": [
 		["Draft", None],
 		["Submitted", "eval:self.docstatus==1"],
-		["Paid", "eval:self.outstanding_amount==0 and self.docstatus==1"],
+		["Return", "eval:self.is_return==1 and self.docstatus==1"],
+		["Credit Note Issued", "eval:self.outstanding_amount < 0 and self.docstatus==1"],
+		["Paid", "eval:self.outstanding_amount==0 and self.docstatus==1 and self.is_return==0"],
 		["Unpaid", "eval:self.outstanding_amount > 0 and getdate(self.due_date) >= getdate(nowdate()) and self.docstatus==1"],
 		["Overdue", "eval:self.outstanding_amount > 0 and getdate(self.due_date) < getdate(nowdate()) and self.docstatus==1"],
 		["Cancelled", "eval:self.docstatus==2"],
@@ -52,7 +54,9 @@
 	"Purchase Invoice": [
 		["Draft", None],
 		["Submitted", "eval:self.docstatus==1"],
-		["Paid", "eval:self.outstanding_amount==0 and self.docstatus==1"],
+		["Return", "eval:self.is_return==1 and self.docstatus==1"],
+		["Debit Note Issued", "eval:self.outstanding_amount < 0 and self.docstatus==1"],
+		["Paid", "eval:self.outstanding_amount==0 and self.docstatus==1 and self.is_return==0"],
 		["Unpaid", "eval:self.outstanding_amount > 0 and getdate(self.due_date) >= getdate(nowdate()) and self.docstatus==1"],
 		["Overdue", "eval:self.outstanding_amount > 0 and getdate(self.due_date) < getdate(nowdate()) and self.docstatus==1"],
 		["Cancelled", "eval:self.docstatus==2"],