refactor: use popup to inform on additional reconciliation step
diff --git a/erpnext/controllers/accounts_controller.py b/erpnext/controllers/accounts_controller.py
index 34eff77..063c1e3 100644
--- a/erpnext/controllers/accounts_controller.py
+++ b/erpnext/controllers/accounts_controller.py
@@ -216,6 +216,18 @@
 					)
 				)
 
+			if self.get("is_return") and self.get("return_against"):
+				document_type = "Credit Note" if self.doctype == "Sales Invoice" else "Debit Note"
+				frappe.msgprint(
+					_(
+						"{0} will be treated as a standalone {0}. Post creation use {1} tool to reconcile against {2}."
+					).format(
+						document_type,
+						get_link_to_form("Payment Reconciliation"),
+						get_link_to_form(self.doctype, self.get("return_against")),
+					)
+				)
+
 			pos_check_field = "is_pos" if self.doctype == "Sales Invoice" else "is_paid"
 			if cint(self.allocate_advances_automatically) and not cint(self.get(pos_check_field)):
 				self.set_advances()