diff --git a/barker/barker/routers/voucher/void.py b/barker/barker/routers/voucher/void.py
index cf1bf6f..0d31118 100644
--- a/barker/barker/routers/voucher/void.py
+++ b/barker/barker/routers/voucher/void.py
@@ -28,7 +28,7 @@ def void(
     try:
         with SessionFuture() as db:
             item: Voucher = db.execute(select(Voucher).where(Voucher.id == id_)).scalar_one()
-            item.reason = reason
+            item.reason = f"{reason} / Old Bill ID was: {item.full_bill_id}"
             item.bill_id = None
             item.voucher_type = VoucherType.VOID
             do_update_settlements(item, [SettleSchema(id=SettleOption.VOID(), amount=round(item.amount))], db)