diff --git a/backend/app/api/routes/events/guests.py b/backend/app/api/routes/events/guests.py
index 07fa513..a13c64f 100644
--- a/backend/app/api/routes/events/guests.py
+++ b/backend/app/api/routes/events/guests.py
@@ -13,6 +13,14 @@ router = APIRouter()
 
 @router.post("/", response_model=GuestRead, operation_id="create_guest")
 def create_guest(guest_in: GuestCreate, db: Session = Depends(get_db)):
+    if guest_in.invitation_code:
+        existing_guest = guest_crud.get_by_invitation_code(db, guest_in.invitation_code)
+        if existing_guest:
+            raise HTTPException(
+                status_code=400, detail="Guest with this invitation code already exists"
+            )
+    else:
+        guest_in.invitation_code = str(uuid.uuid4())[:8]
     guest = guest_crud.create(db, obj_in=guest_in)
     return guest
 
diff --git a/backend/app/crud/guest.py b/backend/app/crud/guest.py
index 73a6533..6ace207 100644
--- a/backend/app/crud/guest.py
+++ b/backend/app/crud/guest.py
@@ -11,6 +11,10 @@ import uuid
 class CRUDGuest(CRUDBase[Guest, GuestCreate, GuestUpdate]):
 
     def create(self, db, obj_in: GuestCreate):
+
+        if obj_in.invitation_code is None:
+            obj_in.invitation_code = str(uuid.uuid4())[:8]
+
         db_guest = Guest(
             event_id=uuid.UUID(obj_in.event_id) if isinstance(obj_in.event_id, str) else obj_in.event_id,  # explicit casting
             invited_by=uuid.UUID(obj_in.invited_by) if isinstance(obj_in.invited_by, str) else obj_in.invited_by,
diff --git a/backend/app/schemas/guests.py b/backend/app/schemas/guests.py
index 0985dfc..44cb411 100644
--- a/backend/app/schemas/guests.py
+++ b/backend/app/schemas/guests.py
@@ -21,7 +21,7 @@ class GuestBase(BaseModel):
 
 
 class GuestCreate(GuestBase):
-    invitation_code: str
+    invitation_code: Optional[str] = None
 
 
 class GuestUpdate(BaseModel):
@@ -45,4 +45,5 @@ class GuestRead(GuestBase):
     response_date: Optional[datetime] = None
     actual_additional_guests: int
     is_blocked: bool
-    model_config = ConfigDict(from_attributes=True)
\ No newline at end of file
+    model_config = ConfigDict(from_attributes=True)
+    invitation_code: str
\ No newline at end of file
diff --git a/backend/tests/api/routes/events/test_guests.py b/backend/tests/api/routes/events/test_guests.py
index d4ef96a..10a9be8 100644
--- a/backend/tests/api/routes/events/test_guests.py
+++ b/backend/tests/api/routes/events/test_guests.py
@@ -39,6 +39,33 @@ class TestGuestsRouter:
         assert data["full_name"] == guest_data["full_name"]
         assert data["email"] == guest_data["email"]
 
+    def test_create_guest_fails_on_duplicate_invitation_code(self, guest_data):
+        # First create the guest successfully
+        response_initial = self.client.post(self.endpoint, json=guest_data)
+        assert response_initial.status_code == 200
+
+        # Attempt to create another guest with the same invitation code
+        new_guest_data = guest_data.copy()
+        new_guest_data["email"] = "new.email@example.com"
+        response_duplicate = self.client.post(self.endpoint, json=new_guest_data)
+
+        assert response_duplicate.status_code == 400
+        assert response_duplicate.json()["detail"] == "Guest with this invitation code already exists"
+
+
+    def test_create_guest_generates_invitation_code_if_not_provided(self, guest_data):
+        # Remove invitation_code to test auto-generation
+        guest_data_without_code = guest_data.copy()
+        guest_data_without_code.pop("invitation_code", None)
+
+        response = self.client.post(self.endpoint, json=guest_data_without_code)
+        assert response.status_code == 200
+
+        data = response.json()
+        print(data)
+        assert "invitation_code" in data
+        assert len(data["invitation_code"]) == 8
+
     def test_create_guest_missing_required_fields_fails(self):
         incomplete_payload = {
             "email": "john.doe@example.com"