diff --git a/barker/barker/routers/voucher/__init__.py b/barker/barker/routers/voucher/__init__.py
index f6c11d5..4ecb050 100644
--- a/barker/barker/routers/voucher/__init__.py
+++ b/barker/barker/routers/voucher/__init__.py
@@ -1,17 +1,16 @@
 import uuid
 
-from datetime import datetime
 from decimal import Decimal
-from typing import List, Set
+from typing import Set
 
 import barker.schemas.voucher as schemas
 
-from barker.models.bill import Bill
 from fastapi import HTTPException, status
 from sqlalchemy import func
 from sqlalchemy.orm import Session
 from sqlalchemy.sql import expression
 
+from ...models.bill import Bill
 from ...models.guest_book import GuestBook
 from ...models.overview import Overview
 from ...models.regime import Regime
diff --git a/barker/barker/routers/voucher/merge_move.py b/barker/barker/routers/voucher/merge_move.py
index 97616cf..180e6f0 100644
--- a/barker/barker/routers/voucher/merge_move.py
+++ b/barker/barker/routers/voucher/merge_move.py
@@ -50,7 +50,20 @@ def merge_kot(
                 .where(Kot.id == data.kot_id, Kot.voucher_id == data.voucher_id)
                 .values(voucher_id=data.new_voucher_id)
             )
-            update_settlements([data.voucher_id, data.new_voucher_id], db)
+            donor: Voucher = db.execute(select(Voucher).where(Voucher.id == data.voucher_id)).scalar_one()
+            recipent: Voucher = db.execute(select(Voucher).where(Voucher.id == data.new_voucher_id)).scalar_one()
+            if has_negatives(donor.kots) or happy_hour_exceeds_regular(donor.kots):
+                raise HTTPException(
+                    status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+                    detail="Donor voucher will have negative products or too many happy hours",
+                )
+            if has_negatives(recipent.kots) or happy_hour_exceeds_regular(recipent.kots):
+                raise HTTPException(
+                    status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+                    detail="Recipient voucher will have negative products or too many happy hours",
+                )
+            do_update_settlements(donor, [], db)
+            do_update_settlements(recipent, [], db)
             db.commit()
     except SQLAlchemyError as e:
         raise HTTPException(
@@ -91,7 +104,19 @@ def move_kot(
             db.flush()
             do_update_bill_numbers(item, db)
             do_update_table(item, None, db)
-            update_settlements([data.voucher_id, item.id], db)
+            donor: Voucher = db.execute(select(Voucher).where(Voucher.id == data.voucher_id)).scalar_one()
+            if has_negatives(donor.kots) or happy_hour_exceeds_regular(donor.kots):
+                raise HTTPException(
+                    status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+                    detail="Donor voucher will have negative products or too many happy hours",
+                )
+            if has_negatives(item.kots) or happy_hour_exceeds_regular(item.kots):
+                raise HTTPException(
+                    status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+                    detail="Recipient voucher will have negative products or too many happy hours",
+                )
+            do_update_settlements(donor, [], db)
+            do_update_settlements(item, [], db)
             db.commit()
     except SQLAlchemyError as e:
         raise HTTPException(
@@ -133,7 +158,8 @@ def merge_table(
             db.execute(delete(Overview).where(Overview.voucher_id == data.voucher_id))
             db.execute(delete(Settlement).where(Settlement.voucher_id == data.voucher_id))
             db.execute(delete(Voucher).where(Voucher.id == data.voucher_id))
-            update_settlements([data.new_voucher_id], db)
+            recipent: Voucher = db.execute(select(Voucher).where(Voucher.id == data.new_voucher_id)).scalar_one()
+            do_update_settlements(recipent, [], db)
             db.commit()
     except SQLAlchemyError as e:
         traceback.print_exc()
@@ -143,12 +169,6 @@ def merge_table(
         )
 
 
-def update_settlements(vouchers: list[uuid.UUID], db: Session):
-    for v in vouchers:
-        voucher: Voucher = db.execute(select(Voucher).where(Voucher.id == v)).scalar_one()
-        do_update_settlements(voucher, [], db)
-
-
 def check_if_voucher_is_unprinted(voucher_id: uuid.UUID, db: Session) -> None:
     voucher_type: VoucherType = db.execute(select(Voucher.voucher_type).where(Voucher.id == voucher_id)).scalar_one()
     if voucher_type is None:
@@ -161,3 +181,26 @@ def check_if_voucher_is_unprinted(voucher_id: uuid.UUID, db: Session) -> None:
             status_code=status.HTTP_403_FORBIDDEN,
             detail="Bill is printed or void.",
         )
+
+
+def has_negatives(kots: list[Kot]) -> bool:
+    inv = [i for k in kots for i in k.inventories]
+    products = set((i.product_id, i.is_happy_hour) for i in inv)
+    for id_, hh in products:
+        quantity = sum(i.quantity for i in inv if i.product_id == id_ and i.is_happy_hour == hh)
+        if quantity < 0:
+            return True
+    return False
+
+
+# This is for the whole bill.  eg. Kot 1 => Reg 2 + HH 2; Kot 2 => Reg 4; Kot 3 => Reg - 4
+# This is pass okay in happy hours items balanced, but overall this is wrong. Hence this check
+def happy_hour_exceeds_regular(kots: list[Kot]) -> bool:
+    inv = [i for k in kots for i in k.inventories]
+    products = set(i.product_id for i in inv if i.is_happy_hour)
+    for p in products:
+        r = sum(i.quantity for i in inv if i.product_id == p and not i.is_happy_hour)
+        h = sum(i.quantity for i in inv if i.product_id == p and i.is_happy_hour)
+        if r < h:
+            return True
+    return False