Holiday entitlement balance to not change until the holiday request has been approved by the line manager

At present an employee submits a holiday request and this automatically is deducted from their total holiday balance before this even reaches the manager to approve/ reject. This is confusing employees who are assuming the holiday has been agreed as it has come off their holiday entitlement balance. Proposal that the holiday balance remains as it is when the holiday is submitted and only changes when it has been approved by manager