diff --git a/models/pos_session.py b/models/pos_session.py
index 4f0ff3f..de33c58 100755
--- a/models/pos_session.py
+++ b/models/pos_session.py
@@ -132,4 +132,22 @@ class PosSession(models.Model):
                 "expected_amount": expected_total,
                 "amount": expected_total,
             })
-        return data
\ No newline at end of file
+        return data
+
+    def _validate_session(self, balancing_account=False, amount_to_balance=0, bank_payment_method_diffs=None):
+        for session in self:
+            if session.config_id.cash_control:
+                difference = session.cash_register_balance_end_real - session.cash_register_balance_end
+                if session.currency_id.compare_amounts(difference, 0.0) > 0:
+                    session.message_post(body="Auto-adjustment: Cashier input %s overridden to expected %s to suppress positive difference of %s." % (
+                        session.currency_id.format(session.cash_register_balance_end_real),
+                        session.currency_id.format(session.cash_register_balance_end),
+                        session.currency_id.format(difference)
+                    ))
+                    session.write({'cash_register_balance_end_real': session.cash_register_balance_end})
+
+            for order in session.order_ids:
+                for payment in order.payment_ids:
+                    if session.currency_id.is_zero(payment.amount):
+                        payment.unlink()
+        return super(PosSession, self)._validate_session(balancing_account, amount_to_balance, bank_payment_method_diffs)
\ No newline at end of file