diff --git a/l10n_es_aeat_mod303/models/mod303.py b/l10n_es_aeat_mod303/models/mod303.py
index 1db71c9d718..84fde10883f 100644
--- a/l10n_es_aeat_mod303/models/mod303.py
+++ b/l10n_es_aeat_mod303/models/mod303.py
@@ -485,7 +485,7 @@ def _compute_result_type(self):
                 if report.devolucion_mensual or report.period_type in ("4T", "12"):
                     if report.use_aeat_account:
                         report.result_type = "V"
-                    elif report.return_last_period:
+                    elif report.return_last_period or report.devolucion_mensual:
                         report.result_type = "D" if report.marca_sepa == "1" else "X"
                     else:
                         report.result_type = "C"