diff --git a/billing/serializers.py b/billing/serializers.py
index 8b613a8..a03bc76 100644
--- a/billing/serializers.py
+++ b/billing/serializers.py
@@ -46,6 +46,7 @@ class TopupSerializer(serializers.ModelSerializer):
             "paid",
             "mib_reference",
             "is_expired",
+            "expires_at",
             "created_at",
             "updated_at",
         ]