diff --git a/lib/serializers/repp/invoice.rb b/lib/serializers/repp/invoice.rb
index 52e09ccb3..686eaac99 100644
--- a/lib/serializers/repp/invoice.rb
+++ b/lib/serializers/repp/invoice.rb
@@ -81,7 +81,6 @@ module Serializers
           total: invoice.total,
           recipient: invoice.buyer.billing_email,
           monthly_invoice: invoice.monthly_invoice,
-          reference_no: invoice.reference_no,
         }
       end
       # rubocop:enable Metrics/MethodLength