[fix] POS, Due Date cannot be before Posting Date
diff --git a/erpnext/accounts/doctype/sales_invoice/pos.py b/erpnext/accounts/doctype/sales_invoice/pos.py
index c659212..419c557 100644
--- a/erpnext/accounts/doctype/sales_invoice/pos.py
+++ b/erpnext/accounts/doctype/sales_invoice/pos.py
@@ -296,9 +296,9 @@
 			if not frappe.db.exists('Sales Invoice', {'offline_pos_name': name}):
 				validate_records(doc)
 				si_doc = frappe.new_doc('Sales Invoice')
-				si_doc.due_date = doc.get('posting_date')
 				si_doc.offline_pos_name = name
 				si_doc.update(doc)
+				si_doc.due_date = doc.get('posting_date')
 				submit_invoice(si_doc, name, doc)
 				name_list.append(name)
 			else:
@@ -404,4 +404,5 @@
 	if not frappe.db.exists('Sales Invoice', {'offline_pos_name': name}):
 		si_doc.docstatus = 0
 		si_doc.flags.ignore_mandatory = True
+		si_doc.due_date = si_doc.posting_date
 		si_doc.insert()