Required modifications done
diff --git a/erpnext/accounts/doctype/sales_invoice/sales_invoice.js b/erpnext/accounts/doctype/sales_invoice/sales_invoice.js
index f679a90..d92f525 100644
--- a/erpnext/accounts/doctype/sales_invoice/sales_invoice.js
+++ b/erpnext/accounts/doctype/sales_invoice/sales_invoice.js
@@ -387,17 +387,15 @@
 }
 
 cur_frm.cscript.on_submit = function(doc, cdt, cdn) {
-	if(cur_frm.doc.is_pos ) {
-		new_doc("Sales Invoice");
-	}
-
-	if(cint(frappe.boot.notification_settings.sales_invoice)) {
-		cur_frm.email_doc(frappe.boot.notification_settings.sales_invoice_message);
-	}
-	
 	$.each(doc["entries"], function(i, row) {
 		if(row.delivery_note) frappe.model.clear_doc("Delivery Note", row.delivery_note)
 	})
+
+	if(cint(frappe.boot.notification_settings.sales_invoice)) {
+		cur_frm.email_doc(frappe.boot.notification_settings.sales_invoice_message);
+	} else if(cur_frm.doc.is_pos) {
+		new_doc("Sales Invoice");
+	}
 }
 
 cur_frm.cscript.send_sms = function() {