(b) it is intended that the property or any part thereof shall cease to be comprised in the settlement; then if the trustees obtain from the Controller a certificate of the amount which in the opinion of the Controller may properly be treated as the prospective amount of the duty, and give the Controller all the information and evidence required by the Controller in connection with the application for the certificate, no person shall be accountable as trustee of the settlement for the duty to which the certificate relates to an amount in excess of the amount certified.