diff --git a/erpnext/accounts/doctype/sales_invoice/sales_invoice.js b/erpnext/accounts/doctype/sales_invoice/sales_invoice.js
index 8daf3f6..d3f142e 100644
--- a/erpnext/accounts/doctype/sales_invoice/sales_invoice.js
+++ b/erpnext/accounts/doctype/sales_invoice/sales_invoice.js
@@ -40,7 +40,9 @@
 		this._super();
 
 		cur_frm.dashboard.reset();
-
+		
+		this.frm.toggle_reqd("due_date", !this.frm.doc.is_return);
+		
 		if(doc.docstatus==1) {
 			cur_frm.add_custom_button('View Ledger', function() {
 				frappe.route_options = {
diff --git a/erpnext/accounts/doctype/sales_invoice/sales_invoice.json b/erpnext/accounts/doctype/sales_invoice/sales_invoice.json
index b983d99..bc6a227 100644
--- a/erpnext/accounts/doctype/sales_invoice/sales_invoice.json
+++ b/erpnext/accounts/doctype/sales_invoice/sales_invoice.json
@@ -156,7 +156,7 @@
    "oldfieldtype": "Date", 
    "permlevel": 0, 
    "read_only": 0, 
-   "reqd": 1, 
+   "reqd": 0, 
    "search_index": 0
   }, 
   {
@@ -1275,7 +1275,7 @@
  "icon": "icon-file-text", 
  "idx": 1, 
  "is_submittable": 1, 
- "modified": "2015-07-17 13:29:36.922418", 
+ "modified": "2015-07-22 16:53:52.995407", 
  "modified_by": "Administrator", 
  "module": "Accounts", 
  "name": "Sales Invoice", 
diff --git a/erpnext/accounts/print_format/credit_note/credit_note.json b/erpnext/accounts/print_format/credit_note/credit_note.json
index de405e6..863d4aa 100644
--- a/erpnext/accounts/print_format/credit_note/credit_note.json
+++ b/erpnext/accounts/print_format/credit_note/credit_note.json
@@ -1,19 +1,19 @@
 {
- "creation": "2014-08-28 11:11:39.796473",
- "disabled": 0,
- "doc_type": "Journal Entry",
- "docstatus": 0,
- "doctype": "Print Format",
- "html": "{%- from \"templates/print_formats/standard_macros.html\" import add_header -%}\n\n<div class=\"page-break\">\n    {%- if not doc.get(\"print_heading\") and not doc.get(\"select_print_heading\") \n        and doc.set(\"select_print_heading\", _(\"Credit Note\")) -%}{%- endif -%}\n    {{ add_header(0, 1, doc, letter_head, no_letterhead) }}\n\n    {%- for label, value in (\n        (_(\"Credit To\"), doc.pay_to_recd_from),\n        (_(\"Date\"), frappe.utils.formatdate(doc.voucher_date)),\n        (_(\"Amount\"), \"<strong>\" + doc.get_formatted(\"total_amount\") + \"</strong><br>\" + (doc.total_amount_in_words or \"\") + \"<br>\"),\n        (_(\"Remarks\"), doc.remark)\n    ) -%}\n\n    <div class=\"row\">\n        <div class=\"col-xs-3\"><label class=\"text-right\">{{ label }}</label></div>\n        <div class=\"col-xs-9\">{{ value }}</div>\n    </div>\n\n    {%- endfor -%}\n\n    <hr>\n    <br>\n    <p class=\"strong\">\n        {{ _(\"For\") }} {{ doc.company }},<br>\n        <br>\n        <br>\n        <br>\n        {{ _(\"Authorized Signatory\") }}\n    </p>\n</div>\n\n\n",
- "idx": 2,
- "modified": "2015-01-12 11:02:25.716825",
- "modified_by": "Administrator",
- "module": "Accounts",
- "name": "Credit Note",
- "owner": "Administrator",
- "parent": "Journal Entry",
- "parentfield": "__print_formats",
- "parenttype": "DocType",
- "print_format_type": "Server",
+ "creation": "2014-08-28 11:11:39.796473", 
+ "custom_format": 0, 
+ "disabled": 0, 
+ "doc_type": "Journal Entry", 
+ "docstatus": 0, 
+ "doctype": "Print Format", 
+ "html": "{%- from \"templates/print_formats/standard_macros.html\" import add_header -%}\n\n<div class=\"page-break\">\n    {%- if not doc.get(\"print_heading\") and not doc.get(\"select_print_heading\") \n        and doc.set(\"select_print_heading\", _(\"Credit Note\")) -%}{%- endif -%}\n    {{ add_header(0, 1, doc, letter_head, no_letterhead) }}\n\n    {%- for label, value in (\n        (_(\"Credit To\"), doc.pay_to_recd_from),\n        (_(\"Date\"), frappe.utils.formatdate(doc.voucher_date)),\n        (_(\"Amount\"), \"<strong>\" + doc.get_formatted(\"total_amount\") + \"</strong><br>\" + (doc.total_amount_in_words or \"\") + \"<br>\"),\n        (_(\"Remarks\"), doc.remark)\n    ) -%}\n\n    <div class=\"row\">\n        <div class=\"col-xs-3\"><label class=\"text-right\">{{ label }}</label></div>\n        <div class=\"col-xs-9\">{{ value }}</div>\n    </div>\n\n    {%- endfor -%}\n\n    <hr>\n    <br>\n    <p class=\"strong\">\n        {{ _(\"For\") }} {{ doc.company }},<br>\n        <br>\n        <br>\n        <br>\n        {{ _(\"Authorized Signatory\") }}\n    </p>\n</div>\n\n\n", 
+ "idx": 2, 
+ "modified": "2015-07-22 17:42:01.560817", 
+ "modified_by": "Administrator", 
+ "name": "Credit Note", 
+ "owner": "Administrator", 
+ "parent": "Journal Entry", 
+ "parentfield": "__print_formats", 
+ "parenttype": "DocType", 
+ "print_format_type": "Server", 
  "standard": "Yes"
-}
+}
\ No newline at end of file
diff --git a/erpnext/accounts/print_format/credit_note___negative_invoice/__init__.py b/erpnext/accounts/print_format/credit_note___negative_invoice/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/erpnext/accounts/print_format/credit_note___negative_invoice/__init__.py
diff --git a/erpnext/accounts/print_format/credit_note___negative_invoice/credit_note___negative_invoice.json b/erpnext/accounts/print_format/credit_note___negative_invoice/credit_note___negative_invoice.json
new file mode 100644
index 0000000..e7d7eab
--- /dev/null
+++ b/erpnext/accounts/print_format/credit_note___negative_invoice/credit_note___negative_invoice.json
@@ -0,0 +1,17 @@
+{
+ "creation": "2015-07-22 17:45:22.220567", 
+ "custom_format": 1, 
+ "disabled": 0, 
+ "doc_type": "Sales Invoice", 
+ "docstatus": 0, 
+ "doctype": "Print Format", 
+ "font": "Default", 
+ "html": "<style>\n\t.print-format table, .print-format tr, \n\t.print-format td, .print-format div, .print-format p {\n\t\tfont-family: Monospace;\n\t\tline-height: 200%;\n\t\tvertical-align: middle;\n\t}\n\t@media screen {\n\t\t.print-format {\n\t\t\twidth: 4in;\n\t\t\tpadding: 0.25in;\n\t\t\tmin-height: 6in;\n\t\t}\n\t}\n</style>\n\n<p class=\"text-center\">\n\t{{ doc.company }}<br>\n\t{{ doc.select_print_heading or _(\"Credit Note\") }}<br>\n</p>\n\n<hr>\n\n{%- for label, value in (\n    (_(\"Receipt No\"), doc.name),\n    (_(\"Date\"), doc.get_formatted(\"posting_date\")),\n\t(_(\"Customer\"), doc.customer_name),\n    (_(\"Amount\"), \"<strong>\" + doc.get_formatted(\"grand_total\", absolute_value=True) + \"</strong><br>\" + (doc.in_words or \"\")),\n\t(_(\"Against\"), doc.return_against),\n    (_(\"Remarks\"), doc.remarks)\n) -%}\n\n\t\t<div class=\"row\">\n\t\t    <div class=\"col-xs-4\"><label class=\"text-right\">{{ label }}</label></div>\n\t\t    <div class=\"col-xs-8\">{{ value }}</div>\n\t\t</div>\n{%- endfor -%}\n\n<hr>\n<br>\n<p class=\"strong\">\n    {{ _(\"For\") }} {{ doc.company }},<br>\n    <br>\n    <br>\n    <br>\n        {{ _(\"Authorized Signatory\") }}\n</p>", 
+ "modified": "2015-07-22 17:45:22.220567", 
+ "modified_by": "Administrator", 
+ "name": "Credit Note - Negative Invoice", 
+ "owner": "Administrator", 
+ "print_format_builder": 0, 
+ "print_format_type": "Server", 
+ "standard": "Yes"
+}
\ No newline at end of file
diff --git a/erpnext/controllers/accounts_controller.py b/erpnext/controllers/accounts_controller.py
index eb7b73f..c094771 100644
--- a/erpnext/controllers/accounts_controller.py
+++ b/erpnext/controllers/accounts_controller.py
@@ -173,6 +173,9 @@
 	def validate_due_date(self):
 		from erpnext.accounts.party import validate_due_date
 		if self.doctype == "Sales Invoice":
+			if not self.due_date:
+				frappe.throw(_("Due Date is mandatory"))
+			
 			validate_due_date(self.posting_date, self.due_date, "Customer", self.customer, self.company)
 		elif self.doctype == "Purchase Invoice":
 			validate_due_date(self.posting_date, self.due_date, "Supplier", self.supplier, self.company)
diff --git a/erpnext/controllers/selling_controller.py b/erpnext/controllers/selling_controller.py
index 01ef605..5ad0a25 100644
--- a/erpnext/controllers/selling_controller.py
+++ b/erpnext/controllers/selling_controller.py
@@ -110,15 +110,14 @@
 		from frappe.utils import money_in_words
 		company_currency = get_company_currency(self.company)
 
-		disable_rounded_total = cint(frappe.db.get_value("Global Defaults", None,
-			"disable_rounded_total"))
+		disable_rounded_total = cint(frappe.db.get_value("Global Defaults", None, "disable_rounded_total"))
 
 		if self.meta.get_field("base_in_words"):
 			self.base_in_words = money_in_words(disable_rounded_total and
-				self.base_grand_total or self.base_rounded_total, company_currency)
+				abs(self.base_grand_total) or abs(self.base_rounded_total), company_currency)
 		if self.meta.get_field("in_words"):
 			self.in_words = money_in_words(disable_rounded_total and
-				self.grand_total or self.rounded_total, self.currency)
+				abs(self.grand_total) or abs(self.rounded_total), self.currency)
 
 	def calculate_commission(self):
 		if self.meta.get_field("commission_rate"):