[update

odex25_realstate/property_management/models/rental_contract.py

@@ -197,7 +197,7 @@ class RentalContract(models.Model):
     # Add Sales Tax Field
     tax_id = fields.Many2one('account.tax', string="Tax", domain=[('type_tax_use', '=', 'sale')])
 
-    @api.onchange('sales_tax_id')
+    @api.onchange('tax_id')
     def _onchange_sales_tax_id(self):
         """
         Apply the selected sales tax to all rent payments when a new tax is selected.