diff --git a/yuthon_property_approval/models/property_lease_contract.py b/yuthon_property_approval/models/property_lease_contract.py
index dad82d42d..6194c1d83 100644
--- a/yuthon_property_approval/models/property_lease_contract.py
+++ b/yuthon_property_approval/models/property_lease_contract.py
@@ -367,6 +367,7 @@ class PropertyLeaseContract(models.Model):
             free_start = start_date + relativedelta(months=self.rent_free_period_month)
             if free_start > end_date:
                 free_start = end_date
+            month_number = (free_start - start_date).days
             self.sudo().write({'breakdown_ids': [(0, 0, {
                 "unit_price": unit_price,
                 "monthly_amount": monthly_amount,