diff --git a/barker/barker/routers/voucher/__init__.py b/barker/barker/routers/voucher/__init__.py
index cd11008..572036b 100644
--- a/barker/barker/routers/voucher/__init__.py
+++ b/barker/barker/routers/voucher/__init__.py
@@ -14,6 +14,7 @@ from sqlalchemy.sql import expression
 
 from ...models.guest_book import GuestBook
 from ...models.overview import Overview
+from ...models.regime import Regime
 from ...models.settle_option import SettleOption
 from ...models.settlement import Settlement
 from ...models.voucher import Voucher
@@ -136,7 +137,8 @@ def do_update_bill_numbers(voucher: Voucher, db: Session) -> bool:
         .where(Bill.voucher_id == voucher.id, Bill.regime_id.in_(old_regimes - regimes))
         .values(is_valid=False)
     )
-
+    if Regime.KOT() not in old_regimes | regimes:
+        regimes.add(Regime.KOT())
     for r in regimes - old_regimes:
         bill_id = db.execute(
             expression.select(func.coalesce(func.max(Bill.bill_number), 0) + 1).where(Bill.regime_id == r)